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 <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: CAI Qian <[email protected]>
Reported-by: CAI Qian <[email protected]>
Signed-off-by: Catalin Marinas <[email protected]>
---
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(-)
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);
}
> @@ -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()")
> - 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);
> }
>
On Wed 12-10-16 10:57:03, Catalin Marinas 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.
Looks good to me
> Fixes: 68f24b08ee89 ("sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK")
> Cc: Andrew Morton <[email protected]>
> Cc: Andy Lutomirski <[email protected]>
> Cc: CAI Qian <[email protected]>
> Reported-by: CAI Qian <[email protected]>
> Signed-off-by: Catalin Marinas <[email protected]>
Acked-by: Michal Hocko <[email protected]>
> ---
>
> 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(-)
>
> 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);
> }
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to [email protected]. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"[email protected]"> [email protected] </a>
--
Michal Hocko
SUSE Labs
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" <[email protected]>
> > To: [email protected]
> > Cc: [email protected], "Andrew Morton" <[email protected]>, "Andy Lutomirski" <[email protected]>,
> > "CAI Qian" <[email protected]>
> > 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 <[email protected]>
> > Cc: Andy Lutomirski <[email protected]>
> > Cc: CAI Qian <[email protected]>
> > Reported-by: CAI Qian <[email protected]>
> > Signed-off-by: Catalin Marinas <[email protected]>
>
> Tested-by: CAI Qian <[email protected]>
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
----- Original Message -----
> From: "Catalin Marinas" <[email protected]>
> To: [email protected]
> Cc: [email protected], "Andrew Morton" <[email protected]>, "Andy Lutomirski" <[email protected]>,
> "CAI Qian" <[email protected]>
> 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 <[email protected]>
> Cc: Andy Lutomirski <[email protected]>
> Cc: CAI Qian <[email protected]>
> Reported-by: CAI Qian <[email protected]>
> Signed-off-by: Catalin Marinas <[email protected]>
Tested-by: CAI Qian <[email protected]>
> ---
>
> 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(-)
>
> 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);
> }
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to [email protected]. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"[email protected]"> [email protected] </a>
>
>
>
On Wed, 12 Oct 2016 10:57:03 +0100 Catalin Marinas <[email protected]> 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 <[email protected]>
> Cc: Andy Lutomirski <[email protected]>
> Cc: CAI Qian <[email protected]>
> Reported-by: CAI Qian <[email protected]>
> Signed-off-by: Catalin Marinas <[email protected]>
I'll add
Cc: <[email protected]> [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 <[email protected]> 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 <[email protected]>
> > Cc: Andy Lutomirski <[email protected]>
> > Cc: CAI Qian <[email protected]>
> > Reported-by: CAI Qian <[email protected]>
> > Signed-off-by: Catalin Marinas <[email protected]>
>
> I'll add
>
> Cc: <[email protected]> [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