pcm_native: result of put_user() needs to be checked

... and no, __put_user() doesn't help here - skipping
access_ok() on the second call does not remove the
possibility of page having become unmapped or r/o
in the meanwhile

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index aef8602..47838f5 100644 (file)
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -3093,7 +3093,8 @@ static int snd_pcm_xferi_frames_ioctl(struct snd_pcm_substream *substream,
                result = snd_pcm_lib_write(substream, xferi.buf, xferi.frames);
        else
                result = snd_pcm_lib_read(substream, xferi.buf, xferi.frames);
-       __put_user(result, &_xferi->result);
+       if (put_user(result, &_xferi->result))
+               return -EFAULT;
        return result < 0 ? result : 0;
 }
 
@@ -3122,7 +3123,8 @@ static int snd_pcm_xfern_frames_ioctl(struct snd_pcm_substream *substream,
        else
                result = snd_pcm_lib_readv(substream, bufs, xfern.frames);
        kfree(bufs);
-       __put_user(result, &_xfern->result);
+       if (put_user(result, &_xfern->result))
+               return -EFAULT;
        return result < 0 ? result : 0;
 }
 
@@ -3137,7 +3139,8 @@ static int snd_pcm_rewind_ioctl(struct snd_pcm_substream *substream,
        if (put_user(0, _frames))
                return -EFAULT;
        result = snd_pcm_rewind(substream, frames);
-       __put_user(result, _frames);
+       if (put_user(result, _frames))
+               return -EFAULT;
        return result < 0 ? result : 0;
 }
 
@@ -3152,7 +3155,8 @@ static int snd_pcm_forward_ioctl(struct snd_pcm_substream *substream,
        if (put_user(0, _frames))
                return -EFAULT;
        result = snd_pcm_forward(substream, frames);
-       __put_user(result, _frames);
+       if (put_user(result, _frames))
+               return -EFAULT;
        return result < 0 ? result : 0;
 }