ALSA: pcm: prevent UAF in snd_pcm_info
diff mbox series

Message ID 20171205171657.74392-1-ndesaulniers@google.com
State New, archived
Headers show
Series
  • ALSA: pcm: prevent UAF in snd_pcm_info
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Commit Message

Nick Desaulniers Dec. 5, 2017, 5:16 p.m. UTC
From: Robb Glasser <rglasser@google.com>

When the device descriptor is closed, the `substream->runtime` pointer
is freed. But another thread may be in the ioctl handler, case
SNDRV_CTL_IOCTL_PCM_INFO. This case calls snd_pcm_info_user() which
calls snd_pcm_info() which accesses the now freed `substream->runtime`.

Signed-off-by: Robb Glasser <rglasser@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 sound/core/pcm.c | 2 ++
 1 file changed, 2 insertions(+)

Comments

Nick Desaulniers Dec. 5, 2017, 5:19 p.m. UTC | #1
+ stable

On Tue, Dec 5, 2017 at 9:16 AM, Nick Desaulniers
<ndesaulniers@google.com> wrote:
> From: Robb Glasser <rglasser@google.com>
>
> When the device descriptor is closed, the `substream->runtime` pointer
> is freed. But another thread may be in the ioctl handler, case
> SNDRV_CTL_IOCTL_PCM_INFO. This case calls snd_pcm_info_user() which
> calls snd_pcm_info() which accesses the now freed `substream->runtime`.
>
> Signed-off-by: Robb Glasser <rglasser@google.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
>  sound/core/pcm.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/sound/core/pcm.c b/sound/core/pcm.c
> index 9070f277f8db..09ee8c6b9f75 100644
> --- a/sound/core/pcm.c
> +++ b/sound/core/pcm.c
> @@ -153,7 +153,9 @@ static int snd_pcm_control_ioctl(struct snd_card *card,
>                                 err = -ENXIO;
>                                 goto _error;
>                         }
> +                       mutex_lock(&pcm->open_mutex);
>                         err = snd_pcm_info_user(substream, info);
> +                       mutex_unlock(&pcm->open_mutex);
>                 _error:
>                         mutex_unlock(&register_mutex);
>                         return err;
> --
> 2.15.0.531.g2ccb3012c9-goog
>
Greg KH Dec. 5, 2017, 5:26 p.m. UTC | #2
On Tue, Dec 05, 2017 at 09:19:32AM -0800, Nick Desaulniers wrote:
> + stable
> 
> On Tue, Dec 5, 2017 at 9:16 AM, Nick Desaulniers
> <ndesaulniers@google.com> wrote:
> > From: Robb Glasser <rglasser@google.com>
> >
> > When the device descriptor is closed, the `substream->runtime` pointer
> > is freed. But another thread may be in the ioctl handler, case
> > SNDRV_CTL_IOCTL_PCM_INFO. This case calls snd_pcm_info_user() which
> > calls snd_pcm_info() which accesses the now freed `substream->runtime`.
> >
> > Signed-off-by: Robb Glasser <rglasser@google.com>
> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> > ---
> >  sound/core/pcm.c | 2 ++
> >  1 file changed, 2 insertions(+)

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>
Takashi Iwai Dec. 5, 2017, 7:14 p.m. UTC | #3
On Tue, 05 Dec 2017 18:16:55 +0100,
Nick Desaulniers wrote:
> 
> From: Robb Glasser <rglasser@google.com>
> 
> When the device descriptor is closed, the `substream->runtime` pointer
> is freed. But another thread may be in the ioctl handler, case
> SNDRV_CTL_IOCTL_PCM_INFO. This case calls snd_pcm_info_user() which
> calls snd_pcm_info() which accesses the now freed `substream->runtime`.
> 
> Signed-off-by: Robb Glasser <rglasser@google.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

Looks reasonable.  Applied with Cc to stable now.


thanks,

Takashi

> ---
>  sound/core/pcm.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/sound/core/pcm.c b/sound/core/pcm.c
> index 9070f277f8db..09ee8c6b9f75 100644
> --- a/sound/core/pcm.c
> +++ b/sound/core/pcm.c
> @@ -153,7 +153,9 @@ static int snd_pcm_control_ioctl(struct snd_card *card,
>  				err = -ENXIO;
>  				goto _error;
>  			}
> +			mutex_lock(&pcm->open_mutex);
>  			err = snd_pcm_info_user(substream, info);
> +			mutex_unlock(&pcm->open_mutex);
>  		_error:
>  			mutex_unlock(&register_mutex);
>  			return err;
> -- 
> 2.15.0.531.g2ccb3012c9-goog
> 
>
Kees Cook Dec. 5, 2017, 7:29 p.m. UTC | #4
On Tue, Dec 5, 2017 at 11:14 AM, Takashi Iwai <tiwai@suse.de> wrote:
> On Tue, 05 Dec 2017 18:16:55 +0100,
> Nick Desaulniers wrote:
>>
>> From: Robb Glasser <rglasser@google.com>
>>
>> When the device descriptor is closed, the `substream->runtime` pointer
>> is freed. But another thread may be in the ioctl handler, case
>> SNDRV_CTL_IOCTL_PCM_INFO. This case calls snd_pcm_info_user() which
>> calls snd_pcm_info() which accesses the now freed `substream->runtime`.
>>
>> Signed-off-by: Robb Glasser <rglasser@google.com>
>> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
>
> Looks reasonable.  Applied with Cc to stable now.

FWIW, this was assigned CVE-2017-0861. (Best to get it into the commit
log if possible.)

-Kees

>
>
> thanks,
>
> Takashi
>
>> ---
>>  sound/core/pcm.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/sound/core/pcm.c b/sound/core/pcm.c
>> index 9070f277f8db..09ee8c6b9f75 100644
>> --- a/sound/core/pcm.c
>> +++ b/sound/core/pcm.c
>> @@ -153,7 +153,9 @@ static int snd_pcm_control_ioctl(struct snd_card *card,
>>                               err = -ENXIO;
>>                               goto _error;
>>                       }
>> +                     mutex_lock(&pcm->open_mutex);
>>                       err = snd_pcm_info_user(substream, info);
>> +                     mutex_unlock(&pcm->open_mutex);
>>               _error:
>>                       mutex_unlock(&register_mutex);
>>                       return err;
>> --
>> 2.15.0.531.g2ccb3012c9-goog
>>
>>
Takashi Iwai Dec. 5, 2017, 10:30 p.m. UTC | #5
On Tue, 05 Dec 2017 20:29:07 +0100,
Kees Cook wrote:
> 
> On Tue, Dec 5, 2017 at 11:14 AM, Takashi Iwai <tiwai@suse.de> wrote:
> > On Tue, 05 Dec 2017 18:16:55 +0100,
> > Nick Desaulniers wrote:
> >>
> >> From: Robb Glasser <rglasser@google.com>
> >>
> >> When the device descriptor is closed, the `substream->runtime` pointer
> >> is freed. But another thread may be in the ioctl handler, case
> >> SNDRV_CTL_IOCTL_PCM_INFO. This case calls snd_pcm_info_user() which
> >> calls snd_pcm_info() which accesses the now freed `substream->runtime`.
> >>
> >> Signed-off-by: Robb Glasser <rglasser@google.com>
> >> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> >
> > Looks reasonable.  Applied with Cc to stable now.
> 
> FWIW, this was assigned CVE-2017-0861. (Best to get it into the commit
> log if possible.)

OK, I updated the changelog.  Thanks for information.


Takashi

Patch
diff mbox series

diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index 9070f277f8db..09ee8c6b9f75 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -153,7 +153,9 @@  static int snd_pcm_control_ioctl(struct snd_card *card,
 				err = -ENXIO;
 				goto _error;
 			}
+			mutex_lock(&pcm->open_mutex);
 			err = snd_pcm_info_user(substream, info);
+			mutex_unlock(&pcm->open_mutex);
 		_error:
 			mutex_unlock(&register_mutex);
 			return err;