path: root/sound
diff options
authorHui Peng <benquike@gmail.com>2018-12-03 16:09:34 +0100
committerTakashi Iwai <tiwai@suse.de>2018-12-03 16:09:38 +0100
commit5f8cf712582617d523120df67d392059eaf2fc4b (patch)
tree7da2be099988c205516860e9bfba4c839df67286 /sound
parent54947cd64c1b8290f64bb2958e343c07270e3a58 (diff)
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 <benquike@gmail.com> Reported-by: Mathias Payer <mathias.payer@nebelwelt.net> Signed-off-by: Hui Peng <benquike@gmail.com> Signed-off-by: Mathias Payer <mathias.payer@nebelwelt.net> Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound')
1 files changed, 4 insertions, 1 deletions
diff --git a/sound/usb/card.c b/sound/usb/card.c
index 2bfe4e80a6b9..a105947eaf55 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -682,9 +682,12 @@ static int usb_audio_probe(struct usb_interface *intf,
if (chip) {
+ /* chip->active is inside the chip->card object,
+ * decrement before memory is possibly returned.
+ */
+ atomic_dec(&chip->active);
if (!chip->num_interfaces)
- atomic_dec(&chip->active);
return err;