| Message ID | 20201218145625.2045-3-tiwai@suse.de (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 618de0f4ef11acd8cf26902e65493d46cc20cc89 |
| Headers | show |
| Series | ALSA: Clear PCM buffers more properly | expand |
On 12/18/20 3:56 PM, Takashi Iwai wrote: > The PCM hw_params core function tries to clear up the PCM buffer > before actually using for avoiding the information leak from the > previous usages or the usage before a new allocation. It performs the > memset() with runtime->dma_bytes, but this might still leave some > remaining bytes untouched; namely, the PCM buffer size is aligned in > page size for mmap, hence runtime->dma_bytes doesn't necessarily cover > all PCM buffer pages, and the remaining bytes are exposed via mmap. > > This patch changes the memory clearance to cover the all buffer pages > if the stream is supposed to be mmap-ready (that guarantees that the > buffer size is aligned in page size). > > Signed-off-by: Takashi Iwai <tiwai@suse.de> Reviewed-by: Lars-Peter Clausen <lars@metafoo.de> > --- > sound/core/pcm_native.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c > index 47b155a49226..9f3f8e953ff0 100644 > --- a/sound/core/pcm_native.c > +++ b/sound/core/pcm_native.c > @@ -755,8 +755,13 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream, > runtime->boundary *= 2; > > /* clear the buffer for avoiding possible kernel info leaks */ > - if (runtime->dma_area && !substream->ops->copy_user) > - memset(runtime->dma_area, 0, runtime->dma_bytes); > + if (runtime->dma_area && !substream->ops->copy_user) { > + size_t size = runtime->dma_bytes; > + > + if (runtime->info & SNDRV_PCM_INFO_MMAP) > + size = PAGE_ALIGN(size); > + memset(runtime->dma_area, 0, size); > + } > > snd_pcm_timer_resolution_change(substream); > snd_pcm_set_state(substream, SNDRV_PCM_STATE_SETUP);
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 47b155a49226..9f3f8e953ff0 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -755,8 +755,13 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream, runtime->boundary *= 2; /* clear the buffer for avoiding possible kernel info leaks */ - if (runtime->dma_area && !substream->ops->copy_user) - memset(runtime->dma_area, 0, runtime->dma_bytes); + if (runtime->dma_area && !substream->ops->copy_user) { + size_t size = runtime->dma_bytes; + + if (runtime->info & SNDRV_PCM_INFO_MMAP) + size = PAGE_ALIGN(size); + memset(runtime->dma_area, 0, size); + } snd_pcm_timer_resolution_change(substream); snd_pcm_set_state(substream, SNDRV_PCM_STATE_SETUP);
The PCM hw_params core function tries to clear up the PCM buffer before actually using for avoiding the information leak from the previous usages or the usage before a new allocation. It performs the memset() with runtime->dma_bytes, but this might still leave some remaining bytes untouched; namely, the PCM buffer size is aligned in page size for mmap, hence runtime->dma_bytes doesn't necessarily cover all PCM buffer pages, and the remaining bytes are exposed via mmap. This patch changes the memory clearance to cover the all buffer pages if the stream is supposed to be mmap-ready (that guarantees that the buffer size is aligned in page size). Signed-off-by: Takashi Iwai <tiwai@suse.de> --- sound/core/pcm_native.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)