linux-kernel - Re: [PATCH v2] riscv: stacktrace: Fix missing the first frame

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Date:   Tue, 3 Jan 2023 11:55:32 -0600
From:   Samuel Holland <samuel@...lland.org>
To:     Liu Shixin <liushixin2@...wei.com>,
        Conor Dooley <conor@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Changbin Du <changbin.du@...el.com>
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] riscv: stacktrace: Fix missing the first frame

On 12/6/22 20:50, Liu Shixin wrote:
> When running kfence_test, I found some testcases failed like this:
> 
>  # test_out_of_bounds_read: EXPECTATION FAILED at mm/kfence/kfence_test.c:346
>  Expected report_matches(&expect) to be true, but is false
>  not ok 1 - test_out_of_bounds_read
> 
> The corresponding call-trace is:
> 
>  BUG: KFENCE: out-of-bounds read in kunit_try_run_case+0x38/0x84
> 
>  Out-of-bounds read at 0x(____ptrval____) (32B right of kfence-#10):
>   kunit_try_run_case+0x38/0x84
>   kunit_generic_run_threadfn_adapter+0x12/0x1e
>   kthread+0xc8/0xde
>   ret_from_exception+0x0/0xc
> 
> The kfence_test using the first frame of call trace to check whether the
> testcase is succeed or not. Commit 6a00ef449370 ("riscv: eliminate
> unreliable __builtin_frame_address(1)") skip first frame for all
> case, which results the kfence_test failed. Indeed, we only need to skip
> the first frame for case (task==NULL || task==current).
> 
> With this patch, the call-trace will be:
> 
>  BUG: KFENCE: out-of-bounds read in test_out_of_bounds_read+0x88/0x19e
> 
>  Out-of-bounds read at 0x(____ptrval____) (1B left of kfence-#7):
>   test_out_of_bounds_read+0x88/0x19e
>   kunit_try_run_case+0x38/0x84
>   kunit_generic_run_threadfn_adapter+0x12/0x1e
>   kthread+0xc8/0xde
>   ret_from_exception+0x0/0xc
> 
> Fixes: 6a00ef449370 ("riscv: eliminate unreliable __builtin_frame_address(1)")
> Signed-off-by: Liu Shixin <liushixin2@...wei.com>
> ---
> v1->v2: Fix the incorrect Fixes tag found by Conor.
> 
>  arch/riscv/kernel/stacktrace.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Tested-by: Samuel Holland <samuel@...lland.org>

Before:

WARNING: CPU: 0 PID: 162 at drivers/regulator/core.c:5700
regulator_unregister+0xf0/0x106
...
[<ffffffff803a0794>] devm_rdev_release+0xe/0x16
[<ffffffff80427bac>] release_nodes+0x3c/0x98
[<ffffffff80428cac>] devres_release_all+0x72/0x9e
[<ffffffff80424054>] device_unbind_cleanup+0x10/0x4a
...

After:

WARNING: CPU: 0 PID: 165 at drivers/regulator/core.c:5700
regulator_unregister+0xf0/0x106
...
[<ffffffff8039d194>] regulator_unregister+0xf0/0x106
[<ffffffff803a0798>] devm_rdev_release+0xe/0x16
[<ffffffff80427bb0>] release_nodes+0x3c/0x98
[<ffffffff80428cb0>] devres_release_all+0x72/0x9e
[<ffffffff80424058>] device_unbind_cleanup+0x10/0x4a
...