linux-kernel - [PATCH 2/5] media: imon: Fix race getting ictx->lock

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Date: Mon, 06 May 2024 21:10:27 +0000
From: Ricardo Ribalda <ribalda@...omium.org>
To: Andy Walls <awalls@...metrocast.net>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>, Sean Young <sean@...s.org>, 
 Jarod Wilson <jarod@...hat.com>
Cc: Hans Verkuil <hverkuil-cisco@...all.nl>, linux-media@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH 2/5] media: imon: Fix race getting ictx->lock

Lets fix a race between mutex_is_lock() and mutex_lock().

<-mutex is not locked
if (!mutex_is_locked(&ictx->lock)) {
	unlock = true; <- mutex is locked externaly
	mutex_lock(&ictx->lock);
}

Let's use mutex_trylock() that does mutex_is_lock() and mutex_lock()
atomically.

Fix the following cocci warning:
drivers/media/rc/imon.c:1167:1-7: preceding lock on line 1153

Fixes: 23ef710e1a6c ("[media] imon: add conditional locking in change_protocol")
Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 drivers/media/rc/imon.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/media/rc/imon.c b/drivers/media/rc/imon.c
index 0b55314a8082..8f1361bcce3a 100644
--- a/drivers/media/rc/imon.c
+++ b/drivers/media/rc/imon.c
@@ -1148,10 +1148,7 @@ static int imon_ir_change_protocol(struct rc_dev *rc, u64 *rc_proto)
 
 	memcpy(ictx->usb_tx_buf, &ir_proto_packet, sizeof(ir_proto_packet));
 
-	if (!mutex_is_locked(&ictx->lock)) {
-		unlock = true;
-		mutex_lock(&ictx->lock);
-	}
+	unlock = mutex_trylock(&ictx->lock);
 
 	retval = send_packet(ictx);
 	if (retval)

-- 
2.45.0.rc1.225.g2a3ae87e7f-goog