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Sat, 25 Jan 2025 19:32:50 -0800 (PST) From: Yunhui Cui To: peterz@infradead.org, mingo@redhat.com, will@kernel.org, boqun.feng@gmail.com, longman@redhat.com, linux-kernel@vger.kernel.org Cc: Yunhui Cui Subject: [PATCH] locking/mutex: add MUTEX_WARN_ON() into fast path Date: Sun, 26 Jan 2025 11:32:43 +0800 Message-Id: <20250126033243.53069-1-cuiyunhui@bytedance.com> X-Mailer: git-send-email 2.39.2 (Apple Git-143) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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!=3D lock) in __mutex_trylock_fast() makes it always happen. Signed-off-by: Yunhui Cui Acked-by: Waiman Long --- 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 =3D (unsigned long)current; unsigned long zero =3D 0UL; =20 + MUTEX_WARN_ON(lock->magic !=3D lock); + if (atomic_long_try_cmpxchg_acquire(&lock->owner, &zero, curr)) return true; =20 --=20 2.39.2