linux-kernel - [PATCH] media: usb: siano: do not free urb-specific transfer buffer

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Message-ID: <20250522140048.2811356-1-n.zhandarovich@fintech.ru>
Date: Thu, 22 May 2025 17:00:47 +0300
From: Nikita Zhandarovich <n.zhandarovich@...tech.ru>
To: Mauro Carvalho Chehab <mchehab@...nel.org>
CC: Nikita Zhandarovich <n.zhandarovich@...tech.ru>, Hans Verkuil
	<hverkuil-cisco@...all.nl>, <linux-media@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <lvc-project@...uxtesting.org>, Hillf Danton
	<hdanton@...a.com>, <syzbot+b466336413a1fba398a5@...kaller.appspotmail.com>
Subject: [PATCH] media: usb: siano: do not free urb-specific transfer buffer

Since siano driver uses separately allocated buffers for urb tranfers,
such as smscore_buffer_t *cb, and deals with them accordingly
via calls to smscore_putbuffer() in smsusb_stop_streaming(), there is
no need to attempt to free urb->transfer_buffer by adding a
URB_FREE_BUFFER to urb transfer flags. As syzkaller shows, it triggers
a warning which will bring about proper crash on systems with
'panic_on_warn' set.

Therefore, skip the flag setting step to fix the issue. This change
was tested exclusively with syz-repros and KMEMLEAK sanitizer.

The idea for this patch was originally devised by Hillf Danton.

Suggested-by: Hillf Danton <hdanton@...a.com>
Reported-by: syzbot+b466336413a1fba398a5@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b466336413a1fba398a5
Fixes: 564246fd3ff4 ("media: siano: Fix coherent memory allocation failure on arm64")
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@...tech.ru>
---
 drivers/media/usb/siano/smsusb.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/media/usb/siano/smsusb.c b/drivers/media/usb/siano/smsusb.c
index 2c8179a84991..a78b1c233aad 100644
--- a/drivers/media/usb/siano/smsusb.c
+++ b/drivers/media/usb/siano/smsusb.c
@@ -168,7 +168,6 @@ static int smsusb_submit_urb(struct smsusb_device_t *dev,
 		smsusb_onresponse,
 		surb
 	);
-	surb->urb->transfer_flags |= URB_FREE_BUFFER;

 	return usb_submit_urb(surb->urb, GFP_ATOMIC);
 }