[PATCH 5.15 232/731] media: imon: fix a race condition in send_packet()

Greg Kroah-Hartman
2022-12-28T14:57:59Z

From: Gautam Menghani <gautammenghani201@gmail.com>

[ Upstream commit 813ceef062b53d68f296aa3cb944b21a091fabdb ]

The function send_packet() has a race condition as follows:

func send_packet()
{
// do work
call usb_submit_urb()
mutex_unlock()
wait_for_event_interruptible() <-- lock gone
mutex_lock()
}

func vfd_write()
{
mutex_lock()
call send_packet() <- prev call is not completed
mutex_unlock()
}

When the mutex is unlocked and the function send_packet() waits for the
call to complete, vfd_write() can start another call, which leads to the
"URB submitted while active" warning in usb_submit_urb().
Fix this by removing the mutex_unlock() call in send_packet() and using
mutex_lock_interruptible().

Link: https://syzkaller.appspot.com/bug?id=e378e6a51fbe6c5cc43e34f131cc9a315ef0337e

Fixes: 21677cfc562a ("V4L/DVB: ir-core: add imon driver")
Reported-by: syzbot+0c3cb6dc05fbbdc3ad66@syzkaller.appspotmail.com
Signed-off-by: Gautam Menghani <gautammenghani201@gmail.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/media/rc/imon.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/media/rc/imon.c b/drivers/media/rc/imon.c
index 97355e3ebdfd..72e4bb0fb71e 100644
--- a/drivers/media/rc/imon.c
+++ b/drivers/media/rc/imon.c
@@ -646,15 +646,14 @@ static int send_packet(struct imon_context *ictx)
pr_err_ratelimited("error submitting urb(%d)\n", retval);
} else {
/* Wait for transmission to complete (or abort) */
- mutex_unlock(&ictx->lock);
retval = wait_for_completion_interruptible(
&ictx->tx.finished);
if (retval) {
usb_kill_urb(ictx->tx_urb);
pr_err_ratelimited("task interrupted\n");
}
- mutex_lock(&ictx->lock);

+ ictx->tx.busy = false;
retval = ictx->tx.status;
if (retval)
pr_err_ratelimited("packet tx failed (%d)\n", retval);
@@ -955,7 +954,8 @@ static ssize_t vfd_write(struct file *file, const char __user *buf,
if (ictx->disconnected)
return -ENODEV;

- mutex_lock(&ictx->lock);
+ if (mutex_lock_interruptible(&ictx->lock))
+ return -ERESTARTSYS;

if (!ictx->dev_present_intf0) {
pr_err_ratelimited("no iMON device present\n");
--
2.35.1