ALSA: usb-audio: Fix UAF decrement if card has no live interfaces in card.c

If a USB sound card reports 0 interfaces, an error condition is triggered
and the function usb_audio_probe errors out. In the error path, there was a
use-after-free vulnerability where the memory object of the card was first
freed, followed by a decrement of the number of active chips. Moving the
decrement above the atomic_dec fixes the UAF.

[ The original problem was introduced in 3.1 kernel, while it was
  developed in a different form.  The Fixes tag below indicates the
  original commit but it doesn't mean that the patch is applicable
  cleanly. -- tiwai ]

Fixes: 362e4e49abe5 ("ALSA: usb-audio - clear chip->probing on error exit")
Reported-by: Hui Peng <[email protected]>
Reported-by: Mathias Payer <[email protected]>
Signed-off-by: Hui Peng <[email protected]>
Signed-off-by: Mathias Payer <[email protected]>
Cc: <[email protected]>
Signed-off-by: Takashi Iwai <[email protected]>

0 files changed, 0 insertions, 0 deletions