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authorKees Cook <keescook@chromium.org>2018-04-10 16:34:53 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-04-11 10:28:37 -0700
commit8f2af155b513583e8b149a384551f13e1ac5dc72 (patch)
treee9a274d97cf4a21f4189343a46b3cd0ddb0e4c79 /arch/parisc
parentd64d01a155f84850f7dc9795f464e3df9a5ddb10 (diff)
downloadop-kernel-dev-8f2af155b513583e8b149a384551f13e1ac5dc72.zip
op-kernel-dev-8f2af155b513583e8b149a384551f13e1ac5dc72.tar.gz
exec: pass stack rlimit into mm layout functions
Patch series "exec: Pin stack limit during exec". Attempts to solve problems with the stack limit changing during exec continue to be frustrated[1][2]. In addition to the specific issues around the Stack Clash family of flaws, Andy Lutomirski pointed out[3] other places during exec where the stack limit is used and is assumed to be unchanging. Given the many places it gets used and the fact that it can be manipulated/raced via setrlimit() and prlimit(), I think the only way to handle this is to move away from the "current" view of the stack limit and instead attach it to the bprm, and plumb this down into the functions that need to know the stack limits. This series implements the approach. [1] 04e35f4495dd ("exec: avoid RLIMIT_STACK races with prlimit()") [2] 779f4e1c6c7c ("Revert "exec: avoid RLIMIT_STACK races with prlimit()"") [3] to security@kernel.org, "Subject: existing rlimit races?" This patch (of 3): Since it is possible that the stack rlimit can change externally during exec (either via another thread calling setrlimit() or another process calling prlimit()), provide a way to pass the rlimit down into the per-architecture mm layout functions so that the rlimit can stay in the bprm structure instead of sitting in the signal structure until exec is finalized. Link: http://lkml.kernel.org/r/1518638796-20819-2-git-send-email-keescook@chromium.org Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: Willy Tarreau <w@1wt.eu> Cc: Hugh Dickins <hughd@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Cc: Rik van Riel <riel@redhat.com> Cc: Laura Abbott <labbott@redhat.com> Cc: Greg KH <greg@kroah.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ben Hutchings <ben.hutchings@codethink.co.uk> Cc: Brad Spengler <spender@grsecurity.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/parisc')
-rw-r--r--arch/parisc/kernel/sys_parisc.c16
1 files changed, 11 insertions, 5 deletions
diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_parisc.c
index 8c99ebb..43b308c 100644
--- a/arch/parisc/kernel/sys_parisc.c
+++ b/arch/parisc/kernel/sys_parisc.c
@@ -70,12 +70,18 @@ static inline unsigned long COLOR_ALIGN(unsigned long addr,
* Top of mmap area (just below the process stack).
*/
-static unsigned long mmap_upper_limit(void)
+/*
+ * When called from arch_get_unmapped_area(), rlim_stack will be NULL,
+ * indicating that "current" should be used instead of a passed-in
+ * value from the exec bprm as done with arch_pick_mmap_layout().
+ */
+static unsigned long mmap_upper_limit(struct rlimit *rlim_stack)
{
unsigned long stack_base;
/* Limit stack size - see setup_arg_pages() in fs/exec.c */
- stack_base = rlimit_max(RLIMIT_STACK);
+ stack_base = rlim_stack ? rlim_stack->rlim_max
+ : rlimit_max(RLIMIT_STACK);
if (stack_base > STACK_SIZE_MAX)
stack_base = STACK_SIZE_MAX;
@@ -127,7 +133,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
info.flags = 0;
info.length = len;
info.low_limit = mm->mmap_legacy_base;
- info.high_limit = mmap_upper_limit();
+ info.high_limit = mmap_upper_limit(NULL);
info.align_mask = last_mmap ? (PAGE_MASK & (SHM_COLOUR - 1)) : 0;
info.align_offset = shared_align_offset(last_mmap, pgoff);
addr = vm_unmapped_area(&info);
@@ -250,10 +256,10 @@ static unsigned long mmap_legacy_base(void)
* This function, called very early during the creation of a new
* process VM image, sets up which VM layout function to use:
*/
-void arch_pick_mmap_layout(struct mm_struct *mm)
+void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
{
mm->mmap_legacy_base = mmap_legacy_base();
- mm->mmap_base = mmap_upper_limit();
+ mm->mmap_base = mmap_upper_limit(rlim_stack);
if (mmap_is_legacy()) {
mm->mmap_base = mm->mmap_legacy_base;
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