From 4af4206be2bd1933cae20c2b6fb2058dbc887f7c Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sun, 13 Apr 2014 20:58:54 +0200 Subject: tracing: Fix syscall_*regfunc() vs copy_process() race syscall_regfunc() and syscall_unregfunc() should set/clear TIF_SYSCALL_TRACEPOINT system-wide, but do_each_thread() can race with copy_process() and miss the new child which was not added to the process/thread lists yet. Change copy_process() to update the child's TIF_SYSCALL_TRACEPOINT under tasklist. Link: http://lkml.kernel.org/p/20140413185854.GB20668@redhat.com Cc: stable@vger.kernel.org # 2.6.33 Fixes: a871bd33a6c0 "tracing: Add syscall tracepoints" Acked-by: Frederic Weisbecker Acked-by: Paul E. McKenney Signed-off-by: Oleg Nesterov Signed-off-by: Steven Rostedt --- kernel/fork.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'kernel') diff --git a/kernel/fork.c b/kernel/fork.c index d2799d1..6a13c46 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1487,7 +1487,9 @@ static struct task_struct *copy_process(unsigned long clone_flags, total_forks++; spin_unlock(¤t->sighand->siglock); + syscall_tracepoint_update(p); write_unlock_irq(&tasklist_lock); + proc_fork_connector(p); cgroup_post_fork(p); if (clone_flags & CLONE_THREAD) -- cgit v1.1 From 8063e41d2ffc0b0ce974ea802158be35902072f3 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sun, 13 Apr 2014 20:59:18 +0200 Subject: tracing: Change syscall_*regfunc() to check PF_KTHREAD and use for_each_process_thread() 1. Remove _irqsafe from syscall_regfunc/syscall_unregfunc, read_lock(tasklist) doesn't need to disable irqs. 2. Change this code to avoid the deprecated do_each_thread() and use for_each_process_thread() (stolen from the patch from Frederic). 3. Change syscall_regfunc() to check PF_KTHREAD to skip the kernel threads, ->mm != NULL is the common mistake. Note: probably this check should be simply removed, needs another patch. [fweisbec@gmail.com: s/do_each_thread/for_each_process_thread/] Link: http://lkml.kernel.org/p/20140413185918.GC20668@redhat.com Signed-off-by: Oleg Nesterov Signed-off-by: Steven Rostedt --- kernel/tracepoint.c | 24 +++++++++++------------- 1 file changed, 11 insertions(+), 13 deletions(-) (limited to 'kernel') diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index 33cbd8c..9cf1264 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -492,33 +492,31 @@ static int sys_tracepoint_refcount; void syscall_regfunc(void) { - unsigned long flags; - struct task_struct *g, *t; + struct task_struct *p, *t; if (!sys_tracepoint_refcount) { - read_lock_irqsave(&tasklist_lock, flags); - do_each_thread(g, t) { + read_lock(&tasklist_lock); + for_each_process_thread(p, t) { /* Skip kernel threads. */ - if (t->mm) + if (!(t->flags & PF_KTHREAD)) set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); - } while_each_thread(g, t); - read_unlock_irqrestore(&tasklist_lock, flags); + } + read_unlock(&tasklist_lock); } sys_tracepoint_refcount++; } void syscall_unregfunc(void) { - unsigned long flags; - struct task_struct *g, *t; + struct task_struct *p, *t; sys_tracepoint_refcount--; if (!sys_tracepoint_refcount) { - read_lock_irqsave(&tasklist_lock, flags); - do_each_thread(g, t) { + read_lock(&tasklist_lock); + for_each_process_thread(p, t) { clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); - } while_each_thread(g, t); - read_unlock_irqrestore(&tasklist_lock, flags); + } + read_unlock(&tasklist_lock); } } #endif -- cgit v1.1 From ea73c79e33c45e1fa0071e216f06fd5682314490 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sun, 13 Apr 2014 20:59:38 +0200 Subject: tracing: syscall_regfunc() should not skip kernel threads syscall_regfunc() ignores the kernel threads because "it has no effect", see cc3b13c1 "Don't trace kernel thread syscalls" which added this check. However, this means that a user-space task spawned by call_usermodehelper() will run without TIF_SYSCALL_TRACEPOINT if sys_tracepoint_refcount != 0. Remove this check. The unnecessary report from ret_from_fork path mentioned by cc3b13c1 is no longer possible, see See commit fb45550d76bb5 "make sure that kernel_thread() callbacks call do_exit() themselves". A kernel_thread() callback can only return and take the int_ret_from_sys_call path after do_execve() succeeds, otherwise the kernel will crash. But in this case it is no longer a kernel thread and thus is needs TIF_SYSCALL_TRACEPOINT. Link: http://lkml.kernel.org/p/20140413185938.GD20668@redhat.com Signed-off-by: Oleg Nesterov Signed-off-by: Steven Rostedt --- kernel/tracepoint.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index 9cf1264..3490407 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -497,9 +497,7 @@ void syscall_regfunc(void) if (!sys_tracepoint_refcount) { read_lock(&tasklist_lock); for_each_process_thread(p, t) { - /* Skip kernel threads. */ - if (!(t->flags & PF_KTHREAD)) - set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); + set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); } read_unlock(&tasklist_lock); } -- cgit v1.1