linux-kernel - Re: [PATCH] locking/mutex: add MUTEX_WARN

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Message-ID: <CAEEQ3wmk5jBOPqD-5GUZ+463mcG919uuKVnBJrWedKLssVDBaA@mail.gmail.com>
Date: Thu, 20 Feb 2025 20:49:50 +0800
From: yunhui cui <cuiyunhui@...edance.com>
To: peterz@...radead.org, mingo@...hat.com, will@...nel.org, 
	boqun.feng@...il.com, longman@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] locking/mutex: add MUTEX_WARN_ON() into fast path

Hi All,

Gentle ping. Any comments on this patch?

On Sun, Jan 26, 2025 at 11:32 AM Yunhui Cui <cuiyunhui@...edance.com> wrote:
>
> Scenario: In platform_device_register, the driver misuses struct
> device as platform_data, making kmemdup duplicate a device. Accessing
> the duplicate may cause list corruption due to its mutex magic or list
> holding old content.
> It recurs randomly as the first mutex - getting process skips the slow
> path and mutex check. Adding MUTEX_WARN_ON(lock->magic!= lock) in
> __mutex_trylock_fast() makes it always happen.
>
> Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
> ---
>  kernel/locking/mutex.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
> index b36f23de48f1..19b636f60a24 100644
> --- a/kernel/locking/mutex.c
> +++ b/kernel/locking/mutex.c
> @@ -143,6 +143,8 @@ static __always_inline bool __mutex_trylock_fast(struct mutex *lock)
>         unsigned long curr = (unsigned long)current;
>         unsigned long zero = 0UL;
>
> +       MUTEX_WARN_ON(lock->magic != lock);
> +
>         if (atomic_long_try_cmpxchg_acquire(&lock->owner, &zero, curr))
>                 return true;
>
> --
> 2.39.2
>

Thanks,
Yunhui