| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.4 01/53] ALSA: pcm: Add missing copy ops check before clearing buffer | Date | Mon, 3 Feb 2020 16:18:53 +0000 |
| |
From: Takashi Iwai <tiwai@suse.de>
[ this is a fix specific to 4.4.y and 4.9.y stable trees; 4.14.y and older already contain the right fix ]
The stable 4.4.y and 4.9.y backports of the upstream commit add9d56d7b37 ("ALSA: pcm: Avoid possible info leaks from PCM stream buffers") dropped the check of substream->ops->copy_user as copy_user is a new member that isn't present in the older kernels. Although upstream drivers should work without this NULL check, it may cause a regression with a downstream driver that sets some inaccessible address to runtime->dma_area, leading to a crash at worst.
Since such drivers must have ops->copy member on older kernels instead of ops->copy_user, this patch adds the missing check of ops->copy for fixing the regression.
Reported-and-tested-by: Andreas Schneider <asn@cryptomilk.org> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- sound/core/pcm_native.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -588,7 +588,7 @@ static int snd_pcm_hw_params(struct snd_ runtime->boundary *= 2; /* clear the buffer for avoiding possible kernel info leaks */ - if (runtime->dma_area) + if (runtime->dma_area && !substream->ops->copy) memset(runtime->dma_area, 0, runtime->dma_bytes); snd_pcm_timer_resolution_change(substream);
|