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Subject[PATCH AUTOSEL 5.4 29/30] media: si470x: Fix use-after-free in si470x_int_in_callback()
Date
From: Shigeru Yoshida <syoshida@redhat.com>

[ Upstream commit 7d21e0b1b41b21d628bf2afce777727bd4479aa5 ]

syzbot reported use-after-free in si470x_int_in_callback() [1]. This
indicates that urb->context, which contains struct si470x_device
object, is freed when si470x_int_in_callback() is called.

The cause of this issue is that si470x_int_in_callback() is called for
freed urb.

si470x_usb_driver_probe() calls si470x_start_usb(), which then calls
usb_submit_urb() and si470x_start(). If si470x_start_usb() fails,
si470x_usb_driver_probe() doesn't kill urb, but it just frees struct
si470x_device object, as depicted below:

si470x_usb_driver_probe()
...
si470x_start_usb()
...
usb_submit_urb()
retval = si470x_start()
return retval
if (retval < 0)
free struct si470x_device object, but don't kill urb

This patch fixes this issue by killing urb when si470x_start_usb()
fails and urb is submitted. If si470x_start_usb() fails and urb is
not submitted, i.e. submitting usb fails, it just frees struct
si470x_device object.

Reported-by: syzbot+9ca7a12fd736d93e0232@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=94ed6dddd5a55e90fd4bab942aa4bb297741d977 [1]
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/media/radio/si470x/radio-si470x-usb.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/media/radio/si470x/radio-si470x-usb.c b/drivers/media/radio/si470x/radio-si470x-usb.c
index 3f8634a46573..1365ae732b79 100644
--- a/drivers/media/radio/si470x/radio-si470x-usb.c
+++ b/drivers/media/radio/si470x/radio-si470x-usb.c
@@ -733,8 +733,10 @@ static int si470x_usb_driver_probe(struct usb_interface *intf,

/* start radio */
retval = si470x_start_usb(radio);
- if (retval < 0)
+ if (retval < 0 && !radio->int_in_running)
goto err_buf;
+ else if (retval < 0) /* in case of radio->int_in_running == 1 */
+ goto err_all;

/* set initial frequency */
si470x_set_freq(radio, 87.5 * FREQ_MUL); /* available in all regions */
--
2.35.1
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