| Commit message (Collapse) | Author | Age | Files | Lines |
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The CPU controller hasn't kept up with the various changes in the whole
cgroup initialization / destruction sequence, and commit:
2e91fa7f6d45 ("cgroup: keep zombies associated with their original cgroups")
caused it to explode.
The reason for this is that zombies do not inhibit css_offline() from
being called, but do stall css_released(). Now we tear down the cfs_rq
structures on css_offline() but zombies can run after that, leading to
use-after-free issues.
The solution is to move the tear-down to css_released(), which
guarantees nobody (including no zombies) is still using our cgroup.
Furthermore, a few simple cleanups are possible too. There doesn't
appear to be any point to us using css_online() (anymore?) so fold that
in css_alloc().
And since cgroup code guarantees an RCU grace period between
css_released() and css_free() we can forgo using call_rcu() and free the
stuff immediately.
Suggested-by: Tejun Heo <tj@kernel.org>
Reported-by: Kazuki Yamaguchi <k@rhe.jp>
Reported-by: Niklas Cassel <niklas.cassel@axis.com>
Tested-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 2e91fa7f6d45 ("cgroup: keep zombies associated with their original cgroups")
Link: http://lkml.kernel.org/r/20160316152245.GY6344@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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On CPU hotplug the steal time accounting can keep a stale rq->prev_steal_time
value over CPU down and up. So after the CPU comes up again the delta
calculation in steal_account_process_tick() wreckages itself due to the
unsigned math:
u64 steal = paravirt_steal_clock(smp_processor_id());
steal -= this_rq()->prev_steal_time;
So if steal is smaller than rq->prev_steal_time we end up with an insane large
value which then gets added to rq->prev_steal_time, resulting in a permanent
wreckage of the accounting. As a consequence the per CPU stats in /proc/stat
become stale.
Nice trick to tell the world how idle the system is (100%) while the CPU is
100% busy running tasks. Though we prefer realistic numbers.
None of the accounting values which use a previous value to account for
fractions is reset at CPU hotplug time. update_rq_clock_task() has a sanity
check for prev_irq_time and prev_steal_time_rq, but that sanity check solely
deals with clock warps and limits the /proc/stat visible wreckage. The
prev_time values are still wrong.
Solution is simple: Reset rq->prev_*_time when the CPU is plugged in again.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: <stable@vger.kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: commit 095c0aa83e52 "sched: adjust scheduler cpu power for stolen time"
Fixes: commit aa483808516c "sched: Remove irq time from available CPU power"
Fixes: commit e6e6685accfa "KVM guest: Steal time accounting"
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1603041539490.3686@nanos
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Use the more common logging method with the eventual goal of removing
pr_warning altogether.
Miscellanea:
- Realign arguments
- Coalesce formats
- Add missing space between a few coalesced formats
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> [kernel/power/suspend.c]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Add a flag to memremap() for writecombine mappings. Mappings satisfied
by this flag will not be cached, however writes may be delayed or
combined into more efficient bursts. This is most suitable for buffers
written sequentially by the CPU for use by other DMA devices.
Signed-off-by: Brian Starkey <brian.starkey@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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These patches implement a MEMREMAP_WC flag for memremap(), which can be
used to obtain writecombine mappings. This is then used for setting up
dma_coherent_mem regions which use the DMA_MEMORY_MAP flag.
The motivation is to fix an alignment fault on arm64, and the suggestion
to implement MEMREMAP_WC for this case was made at [1]. That particular
issue is handled in patch 4, which makes sure that the appropriate
memset function is used when zeroing allocations mapped as IO memory.
This patch (of 4):
Don't modify the flags input argument to memremap(). MEMREMAP_WB is
already a special case so we can check for it directly instead of
clearing flag bits in each mapper.
Signed-off-by: Brian Starkey <brian.starkey@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The value of __ARCH_SI_PREAMBLE_SIZE defines the size (including
padding) of the part of the struct siginfo that is before the union, and
it is then used to calculate the needed padding (SI_PAD_SIZE) to make
the size of struct siginfo equal to 128 (SI_MAX_SIZE) bytes.
Depending on the target architecture and word width it equals to either
3 or 4 times sizeof int.
Since the very beginning we had __ARCH_SI_PREAMBLE_SIZE wrong on the
parisc architecture for the 64bit kernel build. It's even more
frustrating, because it can easily be checked at compile time if the
value was defined correctly.
This patch adds such a check for the correctness of
__ARCH_SI_PREAMBLE_SIZE in the hope that it will prevent existing and
future architectures from running into the same problem.
I refrained from replacing __ARCH_SI_PREAMBLE_SIZE by offsetof() in
copy_siginfo() in include/asm-generic/siginfo.h, because a) it doesn't
make any difference and b) it's used in the Documentation/kmemcheck.txt
example.
I ran this patch through the 0-DAY kernel test infrastructure and only
the parisc architecture triggered as expected. That means that this
patch should be OK for all major architectures.
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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kcov provides code coverage collection for coverage-guided fuzzing
(randomized testing). Coverage-guided fuzzing is a testing technique
that uses coverage feedback to determine new interesting inputs to a
system. A notable user-space example is AFL
(http://lcamtuf.coredump.cx/afl/). However, this technique is not
widely used for kernel testing due to missing compiler and kernel
support.
kcov does not aim to collect as much coverage as possible. It aims to
collect more or less stable coverage that is function of syscall inputs.
To achieve this goal it does not collect coverage in soft/hard
interrupts and instrumentation of some inherently non-deterministic or
non-interesting parts of kernel is disbled (e.g. scheduler, locking).
Currently there is a single coverage collection mode (tracing), but the
API anticipates additional collection modes. Initially I also
implemented a second mode which exposes coverage in a fixed-size hash
table of counters (what Quentin used in his original patch). I've
dropped the second mode for simplicity.
This patch adds the necessary support on kernel side. The complimentary
compiler support was added in gcc revision 231296.
We've used this support to build syzkaller system call fuzzer, which has
found 90 kernel bugs in just 2 months:
https://github.com/google/syzkaller/wiki/Found-Bugs
We've also found 30+ bugs in our internal systems with syzkaller.
Another (yet unexplored) direction where kcov coverage would greatly
help is more traditional "blob mutation". For example, mounting a
random blob as a filesystem, or receiving a random blob over wire.
Why not gcov. Typical fuzzing loop looks as follows: (1) reset
coverage, (2) execute a bit of code, (3) collect coverage, repeat. A
typical coverage can be just a dozen of basic blocks (e.g. an invalid
input). In such context gcov becomes prohibitively expensive as
reset/collect coverage steps depend on total number of basic
blocks/edges in program (in case of kernel it is about 2M). Cost of
kcov depends only on number of executed basic blocks/edges. On top of
that, kernel requires per-thread coverage because there are always
background threads and unrelated processes that also produce coverage.
With inlined gcov instrumentation per-thread coverage is not possible.
kcov exposes kernel PCs and control flow to user-space which is
insecure. But debugfs should not be mapped as user accessible.
Based on a patch by Quentin Casasnovas.
[akpm@linux-foundation.org: make task_struct.kcov_mode have type `enum kcov_mode']
[akpm@linux-foundation.org: unbreak allmodconfig]
[akpm@linux-foundation.org: follow x86 Makefile layout standards]
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: syzkaller <syzkaller@googlegroups.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Tavis Ormandy <taviso@google.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Kees Cook <keescook@google.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: David Drysdale <drysdale@google.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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A couple of functions and variables in the profile implementation are
used only on SMP systems by the procfs code, but are unused if either
procfs is disabled or in uniprocessor kernels. gcc prints a harmless
warning about the unused symbols:
kernel/profile.c:243:13: error: 'profile_flip_buffers' defined but not used [-Werror=unused-function]
static void profile_flip_buffers(void)
^
kernel/profile.c:266:13: error: 'profile_discard_flip_buffers' defined but not used [-Werror=unused-function]
static void profile_discard_flip_buffers(void)
^
kernel/profile.c:330:12: error: 'profile_cpu_callback' defined but not used [-Werror=unused-function]
static int profile_cpu_callback(struct notifier_block *info,
^
This adds further #ifdef to the file, to annotate exactly in which cases
they are used. I have done several thousand ARM randconfig kernels with
this patch applied and no longer get any warnings in this file.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Robin Holt <robinmholt@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Commit 1717f2096b54 ("panic, x86: Fix re-entrance problem due to panic
on NMI") and commit 58c5661f2144 ("panic, x86: Allow CPUs to save
registers even if looping in NMI context") introduced nmi_panic() which
prevents concurrent/recursive execution of panic(). It also saves
registers for the crash dump on x86.
However, there are some cases where NMI handlers still use panic().
This patch set partially replaces them with nmi_panic() in those cases.
Even this patchset is applied, some NMI or similar handlers (e.g. MCE
handler) continue to use panic(). This is because I can't test them
well and actual problems won't happen. For example, the possibility
that normal panic and panic on MCE happen simultaneously is very low.
This patch (of 3):
Convert nmi_panic() to a proper function and export it instead of
exporting internal implementation details to modules, for obvious
reasons.
Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: Javi Merino <javi.merino@arm.com>
Cc: Gobinda Charan Maji <gobinda.cemk07@gmail.com>
Cc: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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This commit fixes the following security hole affecting systems where
all of the following conditions are fulfilled:
- The fs.suid_dumpable sysctl is set to 2.
- The kernel.core_pattern sysctl's value starts with "/". (Systems
where kernel.core_pattern starts with "|/" are not affected.)
- Unprivileged user namespace creation is permitted. (This is
true on Linux >=3.8, but some distributions disallow it by
default using a distro patch.)
Under these conditions, if a program executes under secure exec rules,
causing it to run with the SUID_DUMP_ROOT flag, then unshares its user
namespace, changes its root directory and crashes, the coredump will be
written using fsuid=0 and a path derived from kernel.core_pattern - but
this path is interpreted relative to the root directory of the process,
allowing the attacker to control where a coredump will be written with
root privileges.
To fix the security issue, always interpret core_pattern for dumps that
are written under SUID_DUMP_ROOT relative to the root directory of init.
Signed-off-by: Jann Horn <jann@thejh.net>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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This test-case (simplified version of generated by syzkaller)
#include <unistd.h>
#include <sys/ptrace.h>
#include <sys/wait.h>
void test(void)
{
for (;;) {
if (fork()) {
wait(NULL);
continue;
}
ptrace(PTRACE_SEIZE, getppid(), 0, 0);
ptrace(PTRACE_INTERRUPT, getppid(), 0, 0);
_exit(0);
}
}
int main(void)
{
int np;
for (np = 0; np < 8; ++np)
if (!fork())
test();
while (wait(NULL) > 0)
;
return 0;
}
triggers the 2nd WARN_ON_ONCE(!signr) warning in do_jobctl_trap(). The
problem is that __ptrace_unlink() clears task->jobctl under siglock but
task->ptrace is cleared without this lock held; this fools the "else"
branch which assumes that !PT_SEIZED means PT_PTRACED.
Note also that most of other PTRACE_SEIZE checks can race with detach
from the exiting tracer too. Say, the callers of ptrace_trap_notify()
assume that SEIZED can't go away after it was checked.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Except on SPARC, this is what the code always did. SPARC compat seccomp
was buggy, although the impact of the bug was limited because SPARC
32-bit and 64-bit syscall numbers are the same.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Users of the 32-bit ptrace() ABI expect the full 32-bit ABI. siginfo
translation should check ptrace() ABI, not caller task ABI.
This is an ABI change on SPARC. Let's hope that no one relied on the
old buggy ABI.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Seccomp wants to know the syscall bitness, not the caller task bitness,
when it selects the syscall whitelist.
As far as I know, this makes no difference on any architecture, so it's
not a security problem. (It generates identical code everywhere except
sparc, and, on sparc, the syscall numbering is the same for both ABIs.)
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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When new timeout is written to /proc/sys/kernel/hung_task_timeout_secs,
khungtaskd is interrupted and again sleeps for full timeout duration.
This means that hang task will not be checked if new timeout is written
periodically within old timeout duration and/or checking of hang task
will be delayed for up to previous timeout duration. Fix this by
remembering last time khungtaskd checked hang task.
This change will allow other watchdog tasks (if any) to share khungtaskd
by sleeping for minimal timeout diff of all watchdog tasks. Doing more
watchdog tasks from khungtaskd will reduce the possibility of printk()
collisions by multiple watchdog threads.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup namespace support from Tejun Heo:
"These are changes to implement namespace support for cgroup which has
been pending for quite some time now. It is very straight-forward and
only affects what part of cgroup hierarchies are visible.
After unsharing, mounting a cgroup fs will be scoped to the cgroups
the task belonged to at the time of unsharing and the cgroup paths
exposed to userland would be adjusted accordingly"
* 'for-4.6-ns' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: fix and restructure error handling in copy_cgroup_ns()
cgroup: fix alloc_cgroup_ns() error handling in copy_cgroup_ns()
Add FS_USERNS_FLAG to cgroup fs
cgroup: Add documentation for cgroup namespaces
cgroup: mount cgroupns-root when inside non-init cgroupns
kernfs: define kernfs_node_dentry
cgroup: cgroup namespace setns support
cgroup: introduce cgroup namespaces
sched: new clone flag CLONE_NEWCGROUP for cgroup namespace
kernfs: Add API to generate relative kernfs path
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copy_cgroup_ns()'s error handling was broken and the attempt to fix it
d22025570e2e ("cgroup: fix alloc_cgroup_ns() error handling in
copy_cgroup_ns()") was broken too in that it ended up trying an
ERR_PTR() value.
There's only one place where copy_cgroup_ns() needs to perform cleanup
after failure. Simplify and fix the error handling by removing the
goto's.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
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alloc_cgroup_ns() returns an ERR_PTR value on error but
copy_cgroup_ns() was checking for NULL for error. Fix it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
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allowing root in a non-init user namespace to mount it. This should
now be safe, because
1. non-init-root cannot mount a previously unbound subsystem
2. the task doing the mount must be privileged with respect to the
user namespace owning the cgroup namespace
3. the mounted subsystem will have its current cgroup as the root dentry.
the permissions will be unchanged, so tasks will receive no new
privilege over the cgroups which they did not have on the original
mounts.
Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com>
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This patch enables cgroup mounting inside userns when a process
as appropriate privileges. The cgroup filesystem mounted is
rooted at the cgroupns-root. Thus, in a container-setup, only
the hierarchy under the cgroupns-root is exposed inside the container.
This allows container management tools to run inside the containers
without depending on any global state.
Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
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setns on a cgroup namespace is allowed only if
task has CAP_SYS_ADMIN in its current user-namespace and
over the user-namespace associated with target cgroupns.
No implicit cgroup changes happen with attaching to another
cgroupns. It is expected that the somone moves the attaching
process under the target cgroupns-root.
Signed-off-by: Aditya Kali <adityakali@google.com>
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Introduce the ability to create new cgroup namespace. The newly created
cgroup namespace remembers the cgroup of the process at the point
of creation of the cgroup namespace (referred as cgroupns-root).
The main purpose of cgroup namespace is to virtualize the contents
of /proc/self/cgroup file. Processes inside a cgroup namespace
are only able to see paths relative to their namespace root
(unless they are moved outside of their cgroupns-root, at which point
they will see a relative path from their cgroupns-root).
For a correctly setup container this enables container-tools
(like libcontainer, lxc, lmctfy, etc.) to create completely virtualized
containers without leaking system level cgroup hierarchy to the task.
This patch only implements the 'unshare' part of the cgroupns.
Signed-off-by: Aditya Kali <adityakali@google.com>
Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 protection key support from Ingo Molnar:
"This tree adds support for a new memory protection hardware feature
that is available in upcoming Intel CPUs: 'protection keys' (pkeys).
There's a background article at LWN.net:
https://lwn.net/Articles/643797/
The gist is that protection keys allow the encoding of
user-controllable permission masks in the pte. So instead of having a
fixed protection mask in the pte (which needs a system call to change
and works on a per page basis), the user can map a (handful of)
protection mask variants and can change the masks runtime relatively
cheaply, without having to change every single page in the affected
virtual memory range.
This allows the dynamic switching of the protection bits of large
amounts of virtual memory, via user-space instructions. It also
allows more precise control of MMU permission bits: for example the
executable bit is separate from the read bit (see more about that
below).
This tree adds the MM infrastructure and low level x86 glue needed for
that, plus it adds a high level API to make use of protection keys -
if a user-space application calls:
mmap(..., PROT_EXEC);
or
mprotect(ptr, sz, PROT_EXEC);
(note PROT_EXEC-only, without PROT_READ/WRITE), the kernel will notice
this special case, and will set a special protection key on this
memory range. It also sets the appropriate bits in the Protection
Keys User Rights (PKRU) register so that the memory becomes unreadable
and unwritable.
So using protection keys the kernel is able to implement 'true'
PROT_EXEC on x86 CPUs: without protection keys PROT_EXEC implies
PROT_READ as well. Unreadable executable mappings have security
advantages: they cannot be read via information leaks to figure out
ASLR details, nor can they be scanned for ROP gadgets - and they
cannot be used by exploits for data purposes either.
We know about no user-space code that relies on pure PROT_EXEC
mappings today, but binary loaders could start making use of this new
feature to map binaries and libraries in a more secure fashion.
There is other pending pkeys work that offers more high level system
call APIs to manage protection keys - but those are not part of this
pull request.
Right now there's a Kconfig that controls this feature
(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS) that is default enabled
(like most x86 CPU feature enablement code that has no runtime
overhead), but it's not user-configurable at the moment. If there's
any serious problem with this then we can make it configurable and/or
flip the default"
* 'mm-pkeys-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (38 commits)
x86/mm/pkeys: Fix mismerge of protection keys CPUID bits
mm/pkeys: Fix siginfo ABI breakage caused by new u64 field
x86/mm/pkeys: Fix access_error() denial of writes to write-only VMA
mm/core, x86/mm/pkeys: Add execute-only protection keys support
x86/mm/pkeys: Create an x86 arch_calc_vm_prot_bits() for VMA flags
x86/mm/pkeys: Allow kernel to modify user pkey rights register
x86/fpu: Allow setting of XSAVE state
x86/mm: Factor out LDT init from context init
mm/core, x86/mm/pkeys: Add arch_validate_pkey()
mm/core, arch, powerpc: Pass a protection key in to calc_vm_flag_bits()
x86/mm/pkeys: Actually enable Memory Protection Keys in the CPU
x86/mm/pkeys: Add Kconfig prompt to existing config option
x86/mm/pkeys: Dump pkey from VMA in /proc/pid/smaps
x86/mm/pkeys: Dump PKRU with other kernel registers
mm/core, x86/mm/pkeys: Differentiate instruction fetches
x86/mm/pkeys: Optimize fault handling in access_error()
mm/core: Do not enforce PKEY permissions on remote mm access
um, pkeys: Add UML arch_*_access_permitted() methods
mm/gup, x86/mm/pkeys: Check VMAs and PTEs for protection keys
x86/mm/gup: Simplify get_user_pages() PTE bit handling
...
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A protection key fault is very similar to any other access error.
There must be a VMA, etc... We even want to take the same action
(SIGSEGV) that we do with a normal access fault.
However, we do need to let userspace know that something is
different. We do this the same way what we did with SEGV_BNDERR
with Memory Protection eXtensions (MPX): define a new SEGV code:
SEGV_PKUERR.
We add a siginfo field: si_pkey that reveals to userspace which
protection key was set on the PTE that we faulted on. There is
no other easy way for userspace to figure this out. They could
parse smaps but that would be a bit cruel.
We share space with in siginfo with _addr_bnd. #BR faults from
MPX are completely separate from page faults (#PF) that trigger
from protection key violations, so we never need both at the same
time.
Note that _pkey is a 64-bit value. The current hardware only
supports 4-bit protection keys. We do this because there is
_plenty_ of space in _sigfault and it is possible that future
processors would support more than 4 bits of protection keys.
The x86 code to actually fill in the siginfo is in the next
patch.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Amanieu d'Antras <amanieu@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rik van Riel <riel@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: linux-arch@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20160212210212.3A9B83AC@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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For protection keys, we need to understand whether protections
should be enforced in software or not. In general, we enforce
protections when working on our own task, but not when on others.
We call these "current" and "remote" operations.
This patch introduces a new get_user_pages() variant:
get_user_pages_remote()
Which is a replacement for when get_user_pages() is called on
non-current tsk/mm.
We also introduce a new gup flag: FOLL_REMOTE which can be used
for the "__" gup variants to get this new behavior.
The uprobes is_trap_at_addr() location holds mmap_sem and
calls get_user_pages(current->mm) on an instruction address. This
makes it a pretty unique gup caller. Being an instruction access
and also really originating from the kernel (vs. the app), I opted
to consider this a 'remote' access where protection keys will not
be enforced.
Without protection keys, this patch should not change any behavior.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: jack@suse.cz
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20160212210154.3F0E51EA@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull 'objtool' stack frame validation from Ingo Molnar:
"This tree adds a new kernel build-time object file validation feature
(ONFIG_STACK_VALIDATION=y): kernel stack frame correctness validation.
It was written by and is maintained by Josh Poimboeuf.
The motivation: there's a category of hard to find kernel bugs, most
of them in assembly code (but also occasionally in C code), that
degrades the quality of kernel stack dumps/backtraces. These bugs are
hard to detect at the source code level. Such bugs result in
incorrect/incomplete backtraces most of time - but can also in some
rare cases result in crashes or other undefined behavior.
The build time correctness checking is done via the new 'objtool'
user-space utility that was written for this purpose and which is
hosted in the kernel repository in tools/objtool/. The tool's (very
simple) UI and source code design is shaped after Git and perf and
shares quite a bit of infrastructure with tools/perf (which tooling
infrastructure sharing effort got merged via perf and is already
upstream). Objtool follows the well-known kernel coding style.
Objtool does not try to check .c or .S files, it instead analyzes the
resulting .o generated machine code from first principles: it decodes
the instruction stream and interprets it. (Right now objtool supports
the x86-64 architecture.)
From tools/objtool/Documentation/stack-validation.txt:
"The kernel CONFIG_STACK_VALIDATION option enables a host tool named
objtool which runs at compile time. It has a "check" subcommand
which analyzes every .o file and ensures the validity of its stack
metadata. It enforces a set of rules on asm code and C inline
assembly code so that stack traces can be reliable.
Currently it only checks frame pointer usage, but there are plans to
add CFI validation for C files and CFI generation for asm files.
For each function, it recursively follows all possible code paths
and validates the correct frame pointer state at each instruction.
It also follows code paths involving special sections, like
.altinstructions, __jump_table, and __ex_table, which can add
alternative execution paths to a given instruction (or set of
instructions). Similarly, it knows how to follow switch statements,
for which gcc sometimes uses jump tables."
When this new kernel option is enabled (it's disabled by default), the
tool, if it finds any suspicious assembly code pattern, outputs
warnings in compiler warning format:
warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch
warning: objtool: cik_tiling_mode_table_init()+0x6ce: call without frame pointer save/setup
warning: objtool:__schedule()+0x3c0: duplicate frame pointer save
warning: objtool:__schedule()+0x3fd: sibling call from callable instruction with changed frame pointer
... so that scripts that pick up compiler warnings will notice them.
All known warnings triggered by the tool are fixed by the tree, most
of the commits in fact prepare the kernel to be warning-free. Most of
them are bugfixes or cleanups that stand on their own, but there are
also some annotations of 'special' stack frames for justified cases
such entries to JIT-ed code (BPF) or really special boot time code.
There are two other long-term motivations behind this tool as well:
- To improve the quality and reliability of kernel stack frames, so
that they can be used for optimized live patching.
- To create independent infrastructure to check the correctness of
CFI stack frames at build time. CFI debuginfo is notoriously
unreliable and we cannot use it in the kernel as-is without extra
checking done both on the kernel side and on the build side.
The quality of kernel stack frames matters to debuggability as well,
so IMO we can merge this without having to consider the live patching
or CFI debuginfo angle"
* 'core-objtool-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (52 commits)
objtool: Only print one warning per function
objtool: Add several performance improvements
tools: Copy hashtable.h into tools directory
objtool: Fix false positive warnings for functions with multiple switch statements
objtool: Rename some variables and functions
objtool: Remove superflous INIT_LIST_HEAD
objtool: Add helper macros for traversing instructions
objtool: Fix false positive warnings related to sibling calls
objtool: Compile with debugging symbols
objtool: Detect infinite recursion
objtool: Prevent infinite recursion in noreturn detection
objtool: Detect and warn if libelf is missing and don't break the build
tools: Support relative directory path for 'O='
objtool: Support CROSS_COMPILE
x86/asm/decoder: Use explicitly signed chars
objtool: Enable stack metadata validation on 64-bit x86
objtool: Add CONFIG_STACK_VALIDATION option
objtool: Add tool to perform compile-time stack metadata validation
x86/kprobes: Mark kretprobe_trampoline() stack frame as non-standard
sched: Always inline context_switch()
...
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When CONFIG_GCOV is enabled, gcc decides to put context_switch()
out-of-line, which is inconsistent with its normal behavior.
It also causes an objtool warning because __schedule() no longer inlines
context_switch(), so the "STACK_FRAME_NON_STANDARD(__schedule)"
statement loses its effect.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/d62aee926b6e303394e34a06999a964dc2773cf6.1456719558.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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objtool reports the following warnings for __schedule():
kernel/sched/core.o: warning: objtool:__schedule()+0x3c0: duplicate frame pointer save
kernel/sched/core.o: warning: objtool:__schedule()+0x3fd: sibling call from callable instruction with changed frame pointer
kernel/sched/core.o: warning: objtool:__schedule()+0x40a: call without frame pointer save/setup
kernel/sched/core.o: warning: objtool:__schedule()+0x7fd: frame pointer state mismatch
kernel/sched/core.o: warning: objtool:__schedule()+0x421: frame pointer state mismatch
Basically it's confused by two unusual attributes of the switch_to()
macro:
1. It saves prev's frame pointer to the old stack and restores next's
frame pointer from the new stack.
2. For new tasks it jumps directly to ret_from_fork.
Eventually it would probably be a good idea to clean up the
ret_from_fork hack so that new tasks are created with a valid initial
stack, as suggested by Andy:
https://lkml.kernel.org/r/CALCETrWsqCw4L1qKO9j9L5F+4ED4viuLQTFc=n1pKBZfFPQUFg@mail.gmail.com
Then __schedule() could return normally into the new code and objtool
hopefully wouldn't have a problem anymore.
In the meantime, mark its stack frame as non-standard so we can have a
baseline with no objtool warnings. The marker also serves as a reminder
that this code could be improved a bit.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/91190e324ebd7fcd01748d508d0dfd4693e84d91.1456719558.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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objtool reports the following false positive warnings:
kernel/bpf/core.o: warning: objtool: __bpf_prog_run()+0x5c: sibling call from callable instruction with changed frame pointer
kernel/bpf/core.o: warning: objtool: __bpf_prog_run()+0x60: function has unreachable instruction
kernel/bpf/core.o: warning: objtool: __bpf_prog_run()+0x64: function has unreachable instruction
[...]
It's confused by the following dynamic jump instruction in
__bpf_prog_run()::
jmp *(%r12,%rax,8)
which corresponds to the following line in the C code:
goto *jumptable[insn->code];
There's no way for objtool to deterministically find all possible
branch targets for a dynamic jump, so it can't verify this code.
In this case the jumps all stay within the function, and there's nothing
unusual going on related to the stack, so we can whitelist the function.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Cc: netdev@vger.kernel.org
Link: http://lkml.kernel.org/r/b90e6bf3fdbfb5c4cc1b164b965502e53cf48935.1456719558.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Pull audit updates from Paul Moore:
"A small set of patches for audit this time; just three in total and
one is a spelling fix.
The two patches with actual content are designed to help prevent new
instances of auditd from displacing an existing, functioning auditd
and to generate a log of the attempt. Not to worry, dead/stuck auditd
instances can still be replaced by a new instance without problem.
Nothing controversial, and everything passes our regression suite"
* 'stable-4.6' of git://git.infradead.org/users/pcmoore/audit:
audit: Fix typo in comment
audit: log failed attempts to change audit_pid configuration
audit: stop an old auditd being starved out by a new auditd
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Signed-off-by: Weiyuan <weiyuan.wei@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
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Failed attempts to change the audit_pid configuration are not presently
logged. One case is an attempt to starve an old auditd by starting up
a new auditd when the old one is still alive and active. The other
case is an attempt to orphan a new auditd when an old auditd shuts
down.
Log both as AUDIT_CONFIG_CHANGE messages with failure result.
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <pmoore@redhat.com>
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Nothing prevents a new auditd starting up and replacing a valid
audit_pid when an old auditd is still running, effectively starving out
the old auditd since audit_pid no longer points to the old valid
auditd.
If no message to auditd has been attempted since auditd died
unnaturally or got killed, audit_pid will still indicate it is alive.
There isn't an easy way to detect if an old auditd is still running on
the existing audit_pid other than attempting to send a message to see
if it fails. An -ECONNREFUSED almost certainly means it disappeared
and can be replaced. Other errors are not so straightforward and may
indicate transient problems that will resolve themselves and the old
auditd will recover. Yet others will likely need manual intervention
for which a new auditd will not solve the problem.
Send a new message type (AUDIT_REPLACE) to the old auditd containing a
u32 with the PID of the new auditd. If the audit replace message
succeeds (or doesn't fail with certainty), fail to register the new
auditd and return an error (-EEXIST).
This is expected to make the patch preventing an old auditd orphaning a
new auditd redundant.
V3: Switch audit message type from 1000 to 1300 block.
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <pmoore@redhat.com>
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Pull networking updates from David Miller:
"Highlights:
1) Support more Realtek wireless chips, from Jes Sorenson.
2) New BPF types for per-cpu hash and arrap maps, from Alexei
Starovoitov.
3) Make several TCP sysctls per-namespace, from Nikolay Borisov.
4) Allow the use of SO_REUSEPORT in order to do per-thread processing
of incoming TCP/UDP connections. The muxing can be done using a
BPF program which hashes the incoming packet. From Craig Gallek.
5) Add a multiplexer for TCP streams, to provide a messaged based
interface. BPF programs can be used to determine the message
boundaries. From Tom Herbert.
6) Add 802.1AE MACSEC support, from Sabrina Dubroca.
7) Avoid factorial complexity when taking down an inetdev interface
with lots of configured addresses. We were doing things like
traversing the entire address less for each address removed, and
flushing the entire netfilter conntrack table for every address as
well.
8) Add and use SKB bulk free infrastructure, from Jesper Brouer.
9) Allow offloading u32 classifiers to hardware, and implement for
ixgbe, from John Fastabend.
10) Allow configuring IRQ coalescing parameters on a per-queue basis,
from Kan Liang.
11) Extend ethtool so that larger link mode masks can be supported.
From David Decotigny.
12) Introduce devlink, which can be used to configure port link types
(ethernet vs Infiniband, etc.), port splitting, and switch device
level attributes as a whole. From Jiri Pirko.
13) Hardware offload support for flower classifiers, from Amir Vadai.
14) Add "Local Checksum Offload". Basically, for a tunneled packet
the checksum of the outer header is 'constant' (because with the
checksum field filled into the inner protocol header, the payload
of the outer frame checksums to 'zero'), and we can take advantage
of that in various ways. From Edward Cree"
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next: (1548 commits)
bonding: fix bond_get_stats()
net: bcmgenet: fix dma api length mismatch
net/mlx4_core: Fix backward compatibility on VFs
phy: mdio-thunder: Fix some Kconfig typos
lan78xx: add ndo_get_stats64
lan78xx: handle statistics counter rollover
RDS: TCP: Remove unused constant
RDS: TCP: Add sysctl tunables for sndbuf/rcvbuf on rds-tcp socket
net: smc911x: convert pxa dma to dmaengine
team: remove duplicate set of flag IFF_MULTICAST
bonding: remove duplicate set of flag IFF_MULTICAST
net: fix a comment typo
ethernet: micrel: fix some error codes
ip_tunnels, bpf: define IP_TUNNEL_OPTS_MAX and use it
bpf, dst: add and use dst_tclassid helper
bpf: make skb->tc_classid also readable
net: mvneta: bm: clarify dependencies
cls_bpf: reset class and reuse major in da
ldmvsw: Checkpatch sunvnet.c and sunvnet_common.c
ldmvsw: Add ldmvsw.c driver code
...
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Lots of places in the kernel use memcpy(buf, comm, TASK_COMM_LEN); but
the result is typically passed to print("%s", buf) and extra bytes
after zero don't cause any harm.
In bpf the result of bpf_get_current_comm() is used as the part of
map key and was causing spurious hash map mismatches.
Use strlcpy() to guarantee zero-terminated string.
bpf verifier checks that output buffer is zero-initialized,
so even for short task names the output buffer don't have junk bytes.
Note it's not a security concern, since kprobe+bpf is root only.
Fixes: ffeedafbf023 ("bpf: introduce current->pid, tgid, uid, gid, comm accessors")
Reported-by: Tobias Waldekranz <tobias@waldekranz.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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0-day bot reported build error:
kernel/built-in.o: In function `map_lookup_elem':
>> kernel/bpf/.tmp_syscall.o:(.text+0x329b3c): undefined reference to `bpf_stackmap_copy'
when CONFIG_BPF_SYSCALL is set and CONFIG_PERF_EVENTS is not.
Add weak definition to resolve it.
This code path in map_lookup_elem() is never taken
when CONFIG_PERF_EVENTS is not set.
Fixes: 557c0c6e7df8 ("bpf: convert stackmap to pre-allocation")
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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It was observed that calling bpf_get_stackid() from a kprobe inside
slub or from spin_unlock causes similar deadlock as with hashmap,
therefore convert stackmap to use pre-allocated memory.
The call_rcu is no longer feasible mechanism, since delayed freeing
causes bpf_get_stackid() to fail unpredictably when number of actual
stacks is significantly less than user requested max_entries.
Since elements are no longer freed into slub, we can push elements into
freelist immediately and let them be recycled.
However the very unlikley race between user space map_lookup() and
program-side recycling is possible:
cpu0 cpu1
---- ----
user does lookup(stackidX)
starts copying ips into buffer
delete(stackidX)
calls bpf_get_stackid()
which recyles the element and
overwrites with new stack trace
To avoid user space seeing a partial stack trace consisting of two
merged stack traces, do bucket = xchg(, NULL); copy; xchg(,bucket);
to preserve consistent stack trace delivery to user space.
Now we can move memset(,0) of left-over element value from critical
path of bpf_get_stackid() into slow-path of user space lookup.
Also disallow lookup() from bpf program, since it's useless and
program shouldn't be messing with collected stack trace.
Note that similar race between user space lookup and kernel side updates
is also present in hashmap, but it's not a new race. bpf programs were
always allowed to modify hash and array map elements while user space
is copying them.
Fixes: d5a3b1f69186 ("bpf: introduce BPF_MAP_TYPE_STACK_TRACE")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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If kprobe is placed on spin_unlock then calling kmalloc/kfree from
bpf programs is not safe, since the following dead lock is possible:
kfree->spin_lock(kmem_cache_node->lock)...spin_unlock->kprobe->
bpf_prog->map_update->kmalloc->spin_lock(of the same kmem_cache_node->lock)
and deadlocks.
The following solutions were considered and some implemented, but
eventually discarded
- kmem_cache_create for every map
- add recursion check to slow-path of slub
- use reserved memory in bpf_map_update for in_irq or in preempt_disabled
- kmalloc via irq_work
At the end pre-allocation of all map elements turned out to be the simplest
solution and since the user is charged upfront for all the memory, such
pre-allocation doesn't affect the user space visible behavior.
Since it's impossible to tell whether kprobe is triggered in a safe
location from kmalloc point of view, use pre-allocation by default
and introduce new BPF_F_NO_PREALLOC flag.
While testing of per-cpu hash maps it was discovered
that alloc_percpu(GFP_ATOMIC) has odd corner cases and often
fails to allocate memory even when 90% of it is free.
The pre-allocation of per-cpu hash elements solves this problem as well.
Turned out that bpf_map_update() quickly followed by
bpf_map_lookup()+bpf_map_delete() is very common pattern used
in many of iovisor/bcc/tools, so there is additional benefit of
pre-allocation, since such use cases are must faster.
Since all hash map elements are now pre-allocated we can remove
atomic increment of htab->count and save few more cycles.
Also add bpf_map_precharge_memlock() to check rlimit_memlock early to avoid
large malloc/free done by users who don't have sufficient limits.
Pre-allocation is done with vmalloc and alloc/free is done
via percpu_freelist. Here are performance numbers for different
pre-allocation algorithms that were implemented, but discarded
in favor of percpu_freelist:
1 cpu:
pcpu_ida 2.1M
pcpu_ida nolock 2.3M
bt 2.4M
kmalloc 1.8M
hlist+spinlock 2.3M
pcpu_freelist 2.6M
4 cpu:
pcpu_ida 1.5M
pcpu_ida nolock 1.8M
bt w/smp_align 1.7M
bt no/smp_align 1.1M
kmalloc 0.7M
hlist+spinlock 0.2M
pcpu_freelist 2.0M
8 cpu:
pcpu_ida 0.7M
bt w/smp_align 0.8M
kmalloc 0.4M
pcpu_freelist 1.5M
32 cpu:
kmalloc 0.13M
pcpu_freelist 0.49M
pcpu_ida nolock is a modified percpu_ida algorithm without
percpu_ida_cpu locks and without cross-cpu tag stealing.
It's faster than existing percpu_ida, but not as fast as pcpu_freelist.
bt is a variant of block/blk-mq-tag.c simlified and customized
for bpf use case. bt w/smp_align is using cache line for every 'long'
(similar to blk-mq-tag). bt no/smp_align allocates 'long'
bitmasks continuously to save memory. It's comparable to percpu_ida
and in some cases faster, but slower than percpu_freelist
hlist+spinlock is the simplest free list with single spinlock.
As expeceted it has very bad scaling in SMP.
kmalloc is existing implementation which is still available via
BPF_F_NO_PREALLOC flag. It's significantly slower in single cpu and
in 8 cpu setup it's 3 times slower than pre-allocation with pcpu_freelist,
but saves memory, so in cases where map->max_entries can be large
and number of map update/delete per second is low, it may make
sense to use it.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Introduce simple percpu_freelist to keep single list of elements
spread across per-cpu singly linked lists.
/* push element into the list */
void pcpu_freelist_push(struct pcpu_freelist *, struct pcpu_freelist_node *);
/* pop element from the list */
struct pcpu_freelist_node *pcpu_freelist_pop(struct pcpu_freelist *);
The object is pushed to the current cpu list.
Pop first trying to get the object from the current cpu list,
if it's empty goes to the neigbour cpu list.
For bpf program usage pattern the collision rate is very low,
since programs push and pop the objects typically on the same cpu.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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if kprobe is placed within update or delete hash map helpers
that hold bucket spin lock and triggered bpf program is trying to
grab the spinlock for the same bucket on the same cpu, it will
deadlock.
Fix it by extending existing recursion prevention mechanism.
Note, map_lookup and other tracing helpers don't have this problem,
since they don't hold any locks and don't modify global data.
bpf_trace_printk has its own recursive check and ok as well.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Several cases of overlapping changes, as well as one instance
(vxlan) of a bug fix in 'net' overlapping with code movement
in 'net-next'.
Signed-off-by: David S. Miller <davem@davemloft.net>
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Conflicts:
drivers/net/phy/bcm7xxx.c
drivers/net/phy/marvell.c
drivers/net/vxlan.c
All three conflicts were cases of simple overlapping changes.
Signed-off-by: David S. Miller <davem@davemloft.net>
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Currently, when we pass a buffer from the eBPF stack into a helper
function, the function proto indicates argument types as ARG_PTR_TO_STACK
and ARG_CONST_STACK_SIZE pair. If R<X> contains the former, then R<X+1>
must be of the latter type. Then, verifier checks whether the buffer
points into eBPF stack, is initialized, etc. The verifier also guarantees
that the constant value passed in R<X+1> is greater than 0, so helper
functions don't need to test for it and can always assume a non-NULL
initialized buffer as well as non-0 buffer size.
This patch adds a new argument types ARG_CONST_STACK_SIZE_OR_ZERO that
allows to also pass NULL as R<X> and 0 as R<X+1> into the helper function.
Such helper functions, of course, need to be able to handle these cases
internally then. Verifier guarantees that either R<X> == NULL && R<X+1> == 0
or R<X> != NULL && R<X+1> != 0 (like the case of ARG_CONST_STACK_SIZE), any
other combinations are not possible to load.
I went through various options of extending the verifier, and introducing
the type ARG_CONST_STACK_SIZE_OR_ZERO seems to have most minimal changes
needed to the verifier.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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add new map type to store stack traces and corresponding helper
bpf_get_stackid(ctx, map, flags) - walk user or kernel stack and return id
@ctx: struct pt_regs*
@map: pointer to stack_trace map
@flags: bits 0-7 - numer of stack frames to skip
bit 8 - collect user stack instead of kernel
bit 9 - compare stacks by hash only
bit 10 - if two different stacks hash into the same stackid
discard old
other bits - reserved
Return: >= 0 stackid on success or negative error
stackid is a 32-bit integer handle that can be further combined with
other data (including other stackid) and used as a key into maps.
Userspace will access stackmap using standard lookup/delete syscall commands to
retrieve full stack trace for given stackid.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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. avoid walking the stack when there is no room left in the buffer
. generalize get_perf_callchain() to be called from bpf helper
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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bpf_percpu_hash_update() expects rcu lock to be held and warns if it's not,
which pointed out a missing rcu read lock.
Fixes: 15a07b338 ("bpf: add lookup/update support for per-cpu hash and array maps")
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
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The functions bpf_map_lookup_elem(map, key, value) and
bpf_map_update_elem(map, key, value, flags) need to get/set
values from all-cpus for per-cpu hash and array maps,
so that user space can aggregate/update them as necessary.
Example of single counter aggregation in user space:
unsigned int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
long values[nr_cpus];
long value = 0;
bpf_lookup_elem(fd, key, values);
for (i = 0; i < nr_cpus; i++)
value += values[i];
The user space must provide round_up(value_size, 8) * nr_cpus
array to get/set values, since kernel will use 'long' copy
of per-cpu values to try to copy good counters atomically.
It's a best-effort, since bpf programs and user space are racing
to access the same memory.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Primary use case is a histogram array of latency
where bpf program computes the latency of block requests or other
events and stores histogram of latency into array of 64 elements.
All cpus are constantly running, so normal increment is not accurate,
bpf_xadd causes cache ping-pong and this per-cpu approach allows
fastest collision-free counters.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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