| Message ID | 1476266223-14325-1-git-send-email-catalin.marinas@arm.com |
|---|---|
| State | Accepted |
| Commit | 37df49f433bc3a11f5716fe65aaec5189c6402cb |
| Headers | show |
On Wed, Oct 12, 2016 at 06:16:46PM +0800, Hillf Danton wrote: > > @@ -1453,8 +1453,11 @@ static void kmemleak_scan(void) > > > > read_lock(&tasklist_lock); > > do_each_thread(g, p) { > > Take a look at this commit please. > 1da4db0cd5 ("oom_kill: change oom_kill.c to use for_each_thread()") Thanks. Isn't holding tasklist_lock here enough to avoid such races? -- Catalin
On Wed, Oct 12, 2016 at 11:54:17AM -0400, CAI Qian wrote: > ----- Original Message ----- > > From: "Catalin Marinas" <catalin.marinas@arm.com> > > To: linux-mm@kvack.org > > Cc: linux-kernel@vger.kernel.org, "Andrew Morton" <akpm@linux-foundation.org>, "Andy Lutomirski" <luto@kernel.org>, > > "CAI Qian" <caiqian@redhat.com> > > Sent: Wednesday, October 12, 2016 5:57:03 AM > > Subject: [PATCH] mm: kmemleak: Ensure that the task stack is not freed during scanning > > > > Commit 68f24b08ee89 ("sched/core: Free the stack early if > > CONFIG_THREAD_INFO_IN_TASK") may cause the task->stack to be freed > > during kmemleak_scan() execution, leading to either a NULL pointer > > fault (if task->stack is NULL) or kmemleak accessing already freed > > memory. This patch uses the new try_get_task_stack() API to ensure that > > the task stack is not freed during kmemleak stack scanning. > > > > Fixes: 68f24b08ee89 ("sched/core: Free the stack early if > > CONFIG_THREAD_INFO_IN_TASK") > > Cc: Andrew Morton <akpm@linux-foundation.org> > > Cc: Andy Lutomirski <luto@kernel.org> > > Cc: CAI Qian <caiqian@redhat.com> > > Reported-by: CAI Qian <caiqian@redhat.com> > > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> > > Tested-by: CAI Qian <caiqian@redhat.com> Thanks. BTW, I noticed a few false positives reported by kmemleak with the CONFIG_VMAP_STACK enabled caused by the fact that kmemleak requires two references (instead of one) to a vmalloc'ed object because of the vm_struct already containing the address. The cached_stack[] array only stores the vm_struct rather than the stack address, hence the kmemleak report. I'll work on a fix/annotation. -- Catalin
On Wed, 12 Oct 2016 10:57:03 +0100 Catalin Marinas <catalin.marinas@arm.com> wrote: > Commit 68f24b08ee89 ("sched/core: Free the stack early if > CONFIG_THREAD_INFO_IN_TASK") may cause the task->stack to be freed > during kmemleak_scan() execution, leading to either a NULL pointer > fault (if task->stack is NULL) or kmemleak accessing already freed > memory. This patch uses the new try_get_task_stack() API to ensure that > the task stack is not freed during kmemleak stack scanning. > > Fixes: 68f24b08ee89 ("sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK") > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Andy Lutomirski <luto@kernel.org> > Cc: CAI Qian <caiqian@redhat.com> > Reported-by: CAI Qian <caiqian@redhat.com> > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> I'll add Cc: <stable@vger.kernel.org> [4.8.x]
Hi Andrew, On Wed, Oct 19, 2016 at 11:33:27AM -0700, Andrew Morton wrote: > On Wed, 12 Oct 2016 10:57:03 +0100 Catalin Marinas <catalin.marinas@arm.com> wrote: > > Commit 68f24b08ee89 ("sched/core: Free the stack early if > > CONFIG_THREAD_INFO_IN_TASK") may cause the task->stack to be freed > > during kmemleak_scan() execution, leading to either a NULL pointer > > fault (if task->stack is NULL) or kmemleak accessing already freed > > memory. This patch uses the new try_get_task_stack() API to ensure that > > the task stack is not freed during kmemleak stack scanning. > > > > Fixes: 68f24b08ee89 ("sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK") > > Cc: Andrew Morton <akpm@linux-foundation.org> > > Cc: Andy Lutomirski <luto@kernel.org> > > Cc: CAI Qian <caiqian@redhat.com> > > Reported-by: CAI Qian <caiqian@redhat.com> > > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> > > I'll add > > Cc: <stable@vger.kernel.org> [4.8.x] This should be 4.9.x. The commit that introduces try_get_task_stack() was merged in 4.9-rc1: c6c314a613cd ("sched/core: Add try_get_task_stack() and put_task_stack()"). -- Catalin
diff --git a/mm/kmemleak.c b/mm/kmemleak.c index a5e453cf05c4..e5355a5b423f 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -1453,8 +1453,11 @@ static void kmemleak_scan(void) read_lock(&tasklist_lock); do_each_thread(g, p) { - scan_block(task_stack_page(p), task_stack_page(p) + - THREAD_SIZE, NULL); + void *stack = try_get_task_stack(p); + if (stack) { + scan_block(stack, stack + THREAD_SIZE, NULL); + put_task_stack(p); + } } while_each_thread(g, p); read_unlock(&tasklist_lock); }
Commit 68f24b08ee89 ("sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK") may cause the task->stack to be freed during kmemleak_scan() execution, leading to either a NULL pointer fault (if task->stack is NULL) or kmemleak accessing already freed memory. This patch uses the new try_get_task_stack() API to ensure that the task stack is not freed during kmemleak stack scanning. Fixes: 68f24b08ee89 ("sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK") Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: CAI Qian <caiqian@redhat.com> Reported-by: CAI Qian <caiqian@redhat.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> --- This was reported in a subsequent comment here: https://bugzilla.kernel.org/show_bug.cgi?id=173901 However, the original bugzilla entry doesn't look related to task stack freeing as it was first reported on 4.8-rc8. Andy, sorry for cc'ing you to bugzilla, please feel free to remove your email from the bug above (I can't seem to be able to do it). mm/kmemleak.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)