From: Takashi Iwai <tiwai@suse.de> stable inclusion from stable-v6.6.93 commit 74d90875f3d43f3eff0e9861c4701418795d3455 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/ICGACK CVE: CVE-2025-38078 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- 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> Signed-off-by: Luo Gengkun <luogengkun2@huawei.com> --- include/sound/pcm.h | 2 ++ sound/core/oss/pcm_oss.c | 3 +-- sound/core/pcm_native.c | 11 +++++++++++ 3 files changed, 14 insertions(+), 2 deletions(-) diff --git a/include/sound/pcm.h b/include/sound/pcm.h index 2a815373dac1..ed4449cbdf80 100644 --- a/include/sound/pcm.h +++ b/include/sound/pcm.h @@ -1427,6 +1427,8 @@ int snd_pcm_lib_mmap_iomem(struct snd_pcm_substream *substream, struct vm_area_s #define snd_pcm_lib_mmap_iomem NULL #endif +void snd_pcm_runtime_buffer_set_silence(struct snd_pcm_runtime *runtime); + /** * snd_pcm_limit_isa_dma_size - Get the max size fitting with ISA DMA transfer * @dma: DMA number diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c index 728c211142d1..471de2d1b37a 100644 --- a/sound/core/oss/pcm_oss.c +++ b/sound/core/oss/pcm_oss.c @@ -1085,8 +1085,7 @@ 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 e40de64ec85c..31fc20350fd9 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -703,6 +703,17 @@ 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 -- 2.34.1