forked from luck/tmp_suning_uos_patched
[media] media: usbtv: prevent access to free'd resources
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 Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
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@ -292,6 +292,9 @@ static void snd_usbtv_trigger(struct work_struct *work)
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{
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struct usbtv *chip = container_of(work, struct usbtv, snd_trigger);
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if (!chip->snd)
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return;
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if (atomic_read(&chip->snd_stream))
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usbtv_audio_start(chip);
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else
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@ -392,6 +395,8 @@ int usbtv_audio_init(struct usbtv *usbtv)
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void usbtv_audio_free(struct usbtv *usbtv)
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{
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cancel_work_sync(&usbtv->snd_trigger);
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if (usbtv->snd && usbtv->udev) {
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snd_card_free(usbtv->snd);
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usbtv->snd = NULL;
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