On Wed, Jan 29, 2020 at 10:40:41AM +0100, Takashi Iwai wrote:
[ 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
Thanks for the fix!
greg k-h