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| author | Takashi Iwai <tiwai@suse.de> | 2025-05-16 10:08:16 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-05-29 11:03:20 +0200 |
| commit | bf85e49aaf3a3c5775ea87369ea5f159c2148db4 (patch) | |
| tree | 981f0c0d9b5929ce644aa27027a89ee98b56803e /sound/core | |
| parent | 799d48c95f9b6ea0b2542616c125347903c33801 (diff) | |
| download | linux-bf85e49aaf3a3c5775ea87369ea5f159c2148db4.tar.gz linux-bf85e49aaf3a3c5775ea87369ea5f159c2148db4.tar.bz2 linux-bf85e49aaf3a3c5775ea87369ea5f159c2148db4.zip | |
ALSA: pcm: Fix race of buffer access at PCM OSS layer
commit 93a81ca0657758b607c3f4ba889ae806be9beb73 upstream.
The PCM OSS layer tries to clear the buffer with the silence data at
initialization (or reconfiguration) of a stream with the explicit call
of snd_pcm_format_set_silence() with runtime->dma_area. But this may
lead to a UAF because the accessed runtime->dma_area might be freed
concurrently, as it's performed outside the PCM ops.
For avoiding it, move the code into the PCM core and perform it inside
the buffer access lock, so that it won't be changed during the
operation.
Reported-by: syzbot+32d4647f551007595173@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/68164d8e.050a0220.11da1b.0019.GAE@google.com
Cc: <stable@vger.kernel.org>
Link: https://patch.msgid.link/20250516080817.20068-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'sound/core')
| -rw-r--r-- | sound/core/oss/pcm_oss.c | 3 | ||||
| -rw-r--r-- | sound/core/pcm_native.c | 11 |
2 files changed, 12 insertions, 2 deletions
diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c index 4683b9139c56..4ecb17bd5436 100644 --- a/sound/core/oss/pcm_oss.c +++ b/sound/core/oss/pcm_oss.c @@ -1074,8 +1074,7 @@ static int snd_pcm_oss_change_params_locked(struct snd_pcm_substream *substream) runtime->oss.params = 0; runtime->oss.prepare = 1; runtime->oss.buffer_used = 0; - if (runtime->dma_area) - snd_pcm_format_set_silence(runtime->format, runtime->dma_area, bytes_to_samples(runtime, runtime->dma_bytes)); + snd_pcm_runtime_buffer_set_silence(runtime); runtime->oss.period_frames = snd_pcm_alsa_frames(substream, oss_period_size); diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 0790b5fd917e..0a1ba26872f8 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -723,6 +723,17 @@ static void snd_pcm_buffer_access_unlock(struct snd_pcm_runtime *runtime) atomic_inc(&runtime->buffer_accessing); } +/* fill the PCM buffer with the current silence format; called from pcm_oss.c */ +void snd_pcm_runtime_buffer_set_silence(struct snd_pcm_runtime *runtime) +{ + snd_pcm_buffer_access_lock(runtime); + if (runtime->dma_area) + snd_pcm_format_set_silence(runtime->format, runtime->dma_area, + bytes_to_samples(runtime, runtime->dma_bytes)); + snd_pcm_buffer_access_unlock(runtime); +} +EXPORT_SYMBOL_GPL(snd_pcm_runtime_buffer_set_silence); + #if IS_ENABLED(CONFIG_SND_PCM_OSS) #define is_oss_stream(substream) ((substream)->oss.oss) #else |