[PATCH] stacktrace: check whether task has a stack before saving it

[PATCH] stacktrace: check whether task has a stack before saving it

[Ronald Wahl]

I encountered a crash on ARM32 when trying to dump the stack of some
zombie process. This is caused by a missing check whether the task
actually has a valid stack. This commit adds this check.

Commit 214d8ca6ee85 ("stacktrace: Provide common infrastructure")
introduced this check for platforms that define CONFIG_ARCH_STACKWALK
but ARM32 is not one of them.

Signed-off-by: Ronald Wahl <ronald.wahl@raritan.com>
---
 kernel/stacktrace.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
index 9ed5ce989415..38ae52349306 100644
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -298,6 +298,9 @@ unsigned int stack_trace_save_tsk(struct task_struct *task,
 		.skip	= skipnr + (current == task),
 	};

+	if (!try_get_task_stack(task))
+		return 0;
+
 	save_stack_trace_tsk(task, &trace);
 	return trace.nr_entries;
 }
--
2.41.0

Re: [PATCH] stacktrace: check whether task has a stack before saving it

[Linus Walleij]

On Mon, Oct 30, 2023 at 6:59 PM Ronald Wahl <rwahl@gmx.de> wrote:

> I encountered a crash on ARM32 when trying to dump the stack of some
> zombie process. This is caused by a missing check whether the task
> actually has a valid stack. This commit adds this check.
>
> Commit 214d8ca6ee85 ("stacktrace: Provide common infrastructure")
> introduced this check for platforms that define CONFIG_ARCH_STACKWALK
> but ARM32 is not one of them.
>
> Signed-off-by: Ronald Wahl <ronald.wahl@raritan.com>

Looks correct to me:
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij

Re: [PATCH] stacktrace: check whether task has a stack before saving it

[Ronald Wahl]

On 01.11.23 22:59, Linus Walleij wrote:
> [You don't often get email from linus.walleij@linaro.org. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
>
> On Mon, Oct 30, 2023 at 6:59 PM Ronald Wahl <rwahl@gmx.de> wrote:
>
>> I encountered a crash on ARM32 when trying to dump the stack of some
>> zombie process. This is caused by a missing check whether the task
>> actually has a valid stack. This commit adds this check.
>>
>> Commit 214d8ca6ee85 ("stacktrace: Provide common infrastructure")
>> introduced this check for platforms that define CONFIG_ARCH_STACKWALK
>> but ARM32 is not one of them.
>>
>> Signed-off-by: Ronald Wahl <ronald.wahl@raritan.com>
>
> Looks correct to me:
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Unfortunately it causes a memory leak because I forgot to call
put_task_stack(task) now. Should I post v2 or a separate patch?

- ron


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Re: [PATCH] stacktrace: check whether task has a stack before saving it

[Linus Walleij]

On Mon, Dec 11, 2023 at 2:31 PM Ronald Wahl <ronald.wahl@raritan.com> wrote:

> On 01.11.23 22:59, Linus Walleij wrote:
> > [You don't often get email from linus.walleij@linaro.org. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> >
> > On Mon, Oct 30, 2023 at 6:59 PM Ronald Wahl <rwahl@gmx.de> wrote:
> >
> >> I encountered a crash on ARM32 when trying to dump the stack of some
> >> zombie process. This is caused by a missing check whether the task
> >> actually has a valid stack. This commit adds this check.
> >>
> >> Commit 214d8ca6ee85 ("stacktrace: Provide common infrastructure")
> >> introduced this check for platforms that define CONFIG_ARCH_STACKWALK
> >> but ARM32 is not one of them.
> >>
> >> Signed-off-by: Ronald Wahl <ronald.wahl@raritan.com>
> >
> > Looks correct to me:
> > Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
>
> Unfortunately it causes a memory leak because I forgot to call
> put_task_stack(task) now. Should I post v2 or a separate patch?

Post a v2 I didn't see that anyone applied it?

Yours,
Linus Walleij