From: CAI Qian <caiqian@redhat.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCH] mm: kmemleak: Ensure that the task stack is not freed during scanning
Date: Wed, 12 Oct 2016 11:54:17 -0400 (EDT) [thread overview]
Message-ID: <2086376822.528054.1476287657078.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <1476266223-14325-1-git-send-email-catalin.marinas@arm.com>
----- 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>
> ---
>
> 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 majordomo@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
>
>
>
--
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next prev parent reply other threads:[~2016-10-12 15:54 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-12 9:57 [PATCH] mm: kmemleak: Ensure that the task stack is not freed during scanning Catalin Marinas
2016-10-12 10:16 ` Hillf Danton
2016-10-12 10:47 ` Catalin Marinas
2016-10-12 10:41 ` Michal Hocko
2016-10-12 15:54 ` CAI Qian [this message]
2016-10-12 16:14 ` Catalin Marinas
2016-10-19 18:33 ` Andrew Morton
2016-10-20 10:02 ` Catalin Marinas
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