There is a double-free bug in [snd-usb-audio] module due to alloc/free logic flaw in snd_usb_add_audio_stream() function. This leads to kernel structures corruption and panic. Fix the code flow and alloc/free logic so there is no double-free.
The detailed analysis: https://bugzilla.redhat.com/show_bug.cgi?id=1283358 Reported-by: Ralf Spenneberg <[email protected]> Signed-off-by: Vladis Dronov <[email protected]> --- sound/usb/quirks.c | 17 ++++++++++++----- sound/usb/stream.c | 10 ++++++++-- 2 files changed, 20 insertions(+), 7 deletions(-) diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c index fb62bce..1d41b47 100644 --- a/sound/usb/quirks.c +++ b/sound/usb/quirks.c @@ -164,11 +164,6 @@ static int create_fixed_stream_quirk(struct snd_usb_audio *chip, fp->rate_table = rate_table; } - stream = (fp->endpoint & USB_DIR_IN) - ? SNDRV_PCM_STREAM_CAPTURE : SNDRV_PCM_STREAM_PLAYBACK; - err = snd_usb_add_audio_stream(chip, stream, fp); - if (err < 0) - goto error; if (fp->iface != get_iface_desc(&iface->altsetting[0])->bInterfaceNumber || fp->altset_idx >= iface->num_altsetting) { err = -EINVAL; @@ -181,6 +176,17 @@ static int create_fixed_stream_quirk(struct snd_usb_audio *chip, goto error; } + stream = (fp->endpoint & USB_DIR_IN) + ? SNDRV_PCM_STREAM_CAPTURE : SNDRV_PCM_STREAM_PLAYBACK; + err = snd_usb_add_audio_stream(chip, stream, fp); + if (err < 0) + goto error; + + /* From this point error paths should jump to + * error_after_add_audio_stream: not to error: as fp + * and rate_table will be freed on stream removal + */ + fp->protocol = altsd->bInterfaceProtocol; if (fp->datainterval == 0) @@ -195,6 +201,7 @@ static int create_fixed_stream_quirk(struct snd_usb_audio *chip, error: kfree(fp); kfree(rate_table); + error_after_add_audio_stream: return err; } diff --git a/sound/usb/stream.c b/sound/usb/stream.c index 51258a1..f8ed8b49 100644 --- a/sound/usb/stream.c +++ b/sound/usb/stream.c @@ -349,7 +349,10 @@ int snd_usb_add_audio_stream(struct snd_usb_audio *chip, if (err < 0) return err; snd_usb_init_substream(as, stream, fp); - return add_chmap(as->pcm, stream, subs); + err = add_chmap(as->pcm, stream, subs); + if (err < 0) + list_del_init(&fp->list); + return err; } /* create a new pcm */ @@ -391,7 +394,10 @@ int snd_usb_add_audio_stream(struct snd_usb_audio *chip, snd_usb_proc_pcm_format_add(as); - return add_chmap(pcm, stream, &as->substream[stream]); + err = add_chmap(pcm, stream, &as->substream[stream]); + if (err < 0) + list_del_init(&fp->list); + return err; } static int parse_uac_endpoint_attributes(struct snd_usb_audio *chip, -- 2.5.5
