From: Yunhui Cui Date: Sun, 26 Jan 2025 03:32:43 +0000 (+0800) Subject: locking/mutex: Add MUTEX_WARN_ON() into fast path X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=337369f8ce9e;p=users%2Fhch%2Fmisc.git locking/mutex: Add MUTEX_WARN_ON() into fast path 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 Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20250126033243.53069-1-cuiyunhui@bytedance.com --- 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;