From ea4df33739a3decba670a226d435f312bc42a263 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Wed, 29 Jan 2020 10:40:41 +0100 Subject: ALSA: pcm: Add missing copy ops check before clearing buffer [ 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 Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/pcm_native.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'sound') diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 2376b09c35cf..23e17a58651b 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -588,7 +588,7 @@ 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) + if (runtime->dma_area && !substream->ops->copy) memset(runtime->dma_area, 0, runtime->dma_bytes); snd_pcm_timer_resolution_change(substream); -- cgit v1.2.3