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48e2cfbf98
[ 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
add9d56d7b ("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>