From:   Duoming Zhou <duoming@zju.edu.cn>
To:     linux-media@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, mchehab@kernel.org,
        hverkuil-cisco@xs4all.nl, Duoming Zhou <duoming@zju.edu.cn>
Subject: [PATCH] media: usb: siano: Fix warning due to null work_func_t function pointer
Date:   Wed,  1 Mar 2023 17:18:13 +0800
Message-Id: <20230301091813.82543-1-duoming@zju.edu.cn>
Precedence: bulk

The previous commit ebad8e731c1c ("media: usb: siano: Fix use after
free bugs caused by do_submit_urb") adds cancel_work_sync() in
smsusb_stop_streaming(). But smsusb_stop_streaming() may be called,
even if the work_struct surb->wq has not been initialized. As a result,
the warning will occur. One of the processes that could lead to warning
is shown below:

smsusb_probe()
  smsusb_init_device()
    if (!dev->in_ep || !dev->out_ep || align < 0) {
         smsusb_term_device(intf);
           smsusb_stop_streaming()
             cancel_work_sync(&dev->surbs[i].wq);
               __cancel_work_timer()
                 __flush_work()
                   if (WARN_ON(!work->func)) // work->func is null

The log reported by syzbot is shown below:

WARNING: CPU: 0 PID: 897 at kernel/workqueue.c:3066 __flush_work+0x798/0xa80 kernel/workqueue.c:3063
Modules linked in:
CPU: 0 PID: 897 Comm: kworker/0:2 Not tainted 6.2.0-rc1-syzkaller #0
RIP: 0010:__flush_work+0x798/0xa80 kernel/workqueue.c:3066
...
RSP: 0018:ffffc9000464ebf8 EFLAGS: 00010246
RAX: 1ffff11002dbb420 RBX: 0000000000000021 RCX: 1ffffffff204fa4e
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: ffff888016dda0e8
RBP: ffffc9000464ed98 R08: 0000000000000001 R09: ffffffff90253b2f
R10: 0000000000000001 R11: 0000000000000000 R12: ffff888016dda0e8
R13: ffff888016dda0e8 R14: ffff888016dda100 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd4331efe8 CR3: 000000000b48e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __cancel_work_timer+0x315/0x460 kernel/workqueue.c:3160
 smsusb_stop_streaming drivers/media/usb/siano/smsusb.c:182 [inline]
 smsusb_term_device+0xda/0x2d0 drivers/media/usb/siano/smsusb.c:344
 smsusb_init_device+0x400/0x9ce drivers/media/usb/siano/smsusb.c:419
 smsusb_probe+0xbbd/0xc55 drivers/media/usb/siano/smsusb.c:567
...

This patch adds check before cancel_work_sync(). If surb->wq has not
been initialized, the cancel_work_sync() will not be executed.

Fixes: ebad8e731c1c ("media: usb: siano: Fix use after free bugs caused by do_submit_urb")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
---
 drivers/media/usb/siano/smsusb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/siano/smsusb.c b/drivers/media/usb/siano/smsusb.c
index 6f443c542c6..640737d3b8a 100644
--- a/drivers/media/usb/siano/smsusb.c
+++ b/drivers/media/usb/siano/smsusb.c
@@ -179,7 +179,8 @@ static void smsusb_stop_streaming(struct smsusb_device_t *dev)
 
 	for (i = 0; i < MAX_URBS; i++) {
 		usb_kill_urb(&dev->surbs[i].urb);
-		cancel_work_sync(&dev->surbs[i].wq);
+		if (dev->surbs[i].wq.func)
+			cancel_work_sync(&dev->surbs[i].wq);
 
 		if (dev->surbs[i].cb) {
 			smscore_putbuffer(dev->coredev, dev->surbs[i].cb);
-- 
2.17.1