Messages in this thread Patch in this message | | | From | Matthew Leach <> | Subject | [PATCH] media: usbtv: prevent access to free'd resources | Date | Fri, 8 Jul 2016 13:04:27 +0100 |
| |
When disconnecting the usbtv device, the sound card is unregistered from ALSA and the snd member of the usbtv struct is set to NULL. If the usbtv snd_trigger work is running, this can cause a race condition where the kernel will attempt to access free'd resources, shown in [1].
This patch fixes the disconnection code by cancelling any snd_trigger work before unregistering the sound card from ALSA and checking that the snd member still exists in the work function.
[1]: usb 3-1.2: USB disconnect, device number 6 BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 IP: [<ffffffff81093850>] process_one_work+0x30/0x480 PGD 405bbf067 PUD 405bbe067 PMD 0 Call Trace: [<ffffffff81093ce8>] worker_thread+0x48/0x4e0 [<ffffffff81093ca0>] ? process_one_work+0x480/0x480 [<ffffffff81093ca0>] ? process_one_work+0x480/0x480 [<ffffffff81099998>] kthread+0xd8/0xf0 [<ffffffff815c73c2>] ret_from_fork+0x22/0x40 [<ffffffff810998c0>] ? kthread_worker_fn+0x170/0x170 ---[ end trace 0f3dac5c1a38e610 ]---
Signed-off-by: Matthew Leach <matthew@mattleach.net> Tested-by: Peter Sutton <foxxy@foxdogstudios.com> Cc: stable@vger.kernel.org --- drivers/media/usb/usbtv/usbtv-audio.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/drivers/media/usb/usbtv/usbtv-audio.c b/drivers/media/usb/usbtv/usbtv-audio.c index 78c12d2..5dab024 100644 --- a/drivers/media/usb/usbtv/usbtv-audio.c +++ b/drivers/media/usb/usbtv/usbtv-audio.c @@ -278,6 +278,9 @@ static void snd_usbtv_trigger(struct work_struct *work) { struct usbtv *chip = container_of(work, struct usbtv, snd_trigger); + if (!chip->snd) + return; + if (atomic_read(&chip->snd_stream)) usbtv_audio_start(chip); else @@ -378,6 +381,8 @@ err: void usbtv_audio_free(struct usbtv *usbtv) { + cancel_work_sync(&usbtv->snd_trigger); + if (usbtv->snd && usbtv->udev) { snd_card_free(usbtv->snd); usbtv->snd = NULL; -- 2.9.0
| |