linux-kernel - Re: [PATCH v4 1/2] MIPS: Don't crash in stack

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Message-ID: <aGUmClZQXMIQAIif@alpha.franken.de>
Date: Wed, 2 Jul 2025 14:28:58 +0200
From: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Cc: Brendan Higgins <brendan.higgins@...ux.dev>,
	David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>,
	Huacai Chen <chenhuacai@...nel.org>, linux-mips@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
	kunit-dev@...glegroups.com
Subject: Re: [PATCH v4 1/2] MIPS: Don't crash in stack_top() for tasks
 without ABI or vDSO

On Wed, Jun 11, 2025 at 01:28:26PM +0200, Thomas Weißschuh wrote:
> Not all tasks have an ABI associated or vDSO mapped,
> for example kthreads never do.
> If such a task ever ends up calling stack_top(), it will derefence the
> NULL ABI pointer and crash.
> 
> This can for example happen when using kunit:
> 
>     mips_stack_top+0x28/0xc0
>     arch_pick_mmap_layout+0x190/0x220
>     kunit_vm_mmap_init+0xf8/0x138
>     __kunit_add_resource+0x40/0xa8
>     kunit_vm_mmap+0x88/0xd8
>     usercopy_test_init+0xb8/0x240
>     kunit_try_run_case+0x5c/0x1a8
>     kunit_generic_run_threadfn_adapter+0x28/0x50
>     kthread+0x118/0x240
>     ret_from_kernel_thread+0x14/0x1c
> 
> Only dereference the ABI point if it is set.
> 
> The GIC page is also included as it is specific to the vDSO.
> Also move the randomization adjustment into the same conditional.
> 
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
> Reviewed-by: David Gow <davidgow@...gle.com>
> ---
>  arch/mips/kernel/process.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)

applied to mips-next.

Thomas.

-- 
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