linux-kernel - [tip: locking/core] locking/mutex: Add MUTEX_WARN

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Message-ID: <174016613836.10177.12534349520958572441.tip-bot2@tip-bot2>
Date: Fri, 21 Feb 2025 19:28:58 -0000
From: "tip-bot2 for Yunhui Cui" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Yunhui Cui <cuiyunhui@...edance.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: locking/core] locking/mutex: Add MUTEX_WARN_ON() into fast path

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     337369f8ce9e20226402cf139c4f0d3ada7d1705
Gitweb:        https://git.kernel.org/tip/337369f8ce9e20226402cf139c4f0d3ada7d1705
Author:        Yunhui Cui <cuiyunhui@...edance.com>
AuthorDate:    Sun, 26 Jan 2025 11:32:43 +08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Fri, 21 Feb 2025 20:19:12 +01:00

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 <cuiyunhui@...edance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20250126033243.53069-1-cuiyunhui@bytedance.com
---
 kernel/locking/mutex.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index b36f23d..19b636f 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;