| Message ID | 20190724121327.9894-1-baijiaju1990@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ALSA: core: Fix possible null-pointer dereferences in snd_timer_proc_read() | expand |
On Wed, 24 Jul 2019 14:13:27 +0200, Jia-Ju Bai wrote: > > In snd_timer_proc_read(), there is an if statement on line 1204 to check > whether timer->card is NULL: > if (timer->card && timer->card->shutdown) > > When timer->card is NULL, it is used on lines 1212 and 1215: > timer->card->number > > Thus, possible null-pointer dereferences may occur. > > To fix these bugs, timer->card is checked before being used. Both cases can (should) never happen. The SNDRV_TIMER_CLASS_CARD is always associated with a timer with a card object. Ditto for SNDRV_TIMER_CLASS_PCM, where a PCM is always tied with a card. So, if any, this should be a WARN_ON(). But I doubt it being any useful. thanks, Takashi > > These bugs are found by a static analysis tool STCheck written by us. > > Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com> > --- > sound/core/timer.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/sound/core/timer.c b/sound/core/timer.c > index 5c9fbf3f4340..967d06a3cdec 100644 > --- a/sound/core/timer.c > +++ b/sound/core/timer.c > @@ -1208,11 +1208,13 @@ static void snd_timer_proc_read(struct snd_info_entry *entry, > snd_iprintf(buffer, "G%i: ", timer->tmr_device); > break; > case SNDRV_TIMER_CLASS_CARD: > - snd_iprintf(buffer, "C%i-%i: ", > - timer->card->number, timer->tmr_device); > + snd_iprintf(buffer, "C%i-%i: ", > + timer->card ? timer->card->number : -1, > + timer->tmr_device); > break; > case SNDRV_TIMER_CLASS_PCM: > - snd_iprintf(buffer, "P%i-%i-%i: ", timer->card->number, > + snd_iprintf(buffer, "P%i-%i-%i: ", > + timer->card ? timer->card->number : -1, > timer->tmr_device, timer->tmr_subdevice); > break; > default: > -- > 2.17.0 > >
diff --git a/sound/core/timer.c b/sound/core/timer.c index 5c9fbf3f4340..967d06a3cdec 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1208,11 +1208,13 @@ static void snd_timer_proc_read(struct snd_info_entry *entry, snd_iprintf(buffer, "G%i: ", timer->tmr_device); break; case SNDRV_TIMER_CLASS_CARD: - snd_iprintf(buffer, "C%i-%i: ", - timer->card->number, timer->tmr_device); + snd_iprintf(buffer, "C%i-%i: ", + timer->card ? timer->card->number : -1, + timer->tmr_device); break; case SNDRV_TIMER_CLASS_PCM: - snd_iprintf(buffer, "P%i-%i-%i: ", timer->card->number, + snd_iprintf(buffer, "P%i-%i-%i: ", + timer->card ? timer->card->number : -1, timer->tmr_device, timer->tmr_subdevice); break; default:
In snd_timer_proc_read(), there is an if statement on line 1204 to check whether timer->card is NULL: if (timer->card && timer->card->shutdown) When timer->card is NULL, it is used on lines 1212 and 1215: timer->card->number Thus, possible null-pointer dereferences may occur. To fix these bugs, timer->card is checked before being used. These bugs are found by a static analysis tool STCheck written by us. Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com> --- sound/core/timer.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)