ALSA: core: don't return uninitialized snd_compr_tstamp

The snd_compr_update_tstamp() can only fill in the snd_compr_tstamp
if the codec implements the pointer() function. If that happened
the code was previously returning uninitialized garbage in the
tstamp because it wasn't initialized anywhere.

This change zero-fills the tstamp in the two places it is used
before calling snd_compr_update_tstamp(), and also has
snd_compr_update_tstamp() return an error indication if it
can't provide a tstamp. For the case of snd_compr_calc_avail()
it ignores this error because we still need to return info on
the available buffer space even if we can't provide tstamp
info - when the tstamp is not valid all fields are now
guaranteed to be zero.

Signed-off-by: Richard Fitzgerald <rf@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 12 insertions, 6 deletions

diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
index ad11dc994792..2d620688cfb7 100644
--- a/sound/core/compress_offload.c
+++ b/sound/core/compress_offload.c
@@ -144,16 +144,17 @@ static int snd_compr_free(struct inode *inode, struct file *f)
         return 0;
 }
 
-static void snd_compr_update_tstamp(struct snd_compr_stream *stream,
+static int snd_compr_update_tstamp(struct snd_compr_stream *stream,
                 struct snd_compr_tstamp *tstamp)
 {
         if (!stream->ops->pointer)
-                return;
+                return -ENOTSUPP;
         stream->ops->pointer(stream, tstamp);
         pr_debug("dsp consumed till %d total %d bytes\n",
                 tstamp->byte_offset, tstamp->copied_total);
         stream->runtime->hw_pointer = tstamp->byte_offset;
         stream->runtime->total_bytes_transferred = tstamp->copied_total;
+        return 0;
 }
 
 static size_t snd_compr_calc_avail(struct snd_compr_stream *stream,
@@ -161,7 +162,9 @@ static size_t snd_compr_calc_avail(struct snd_compr_stream *stream,
 {
         long avail_calc; /*this needs to be signed variable */
 
+        memset(avail, 0, sizeof(*avail));
         snd_compr_update_tstamp(stream, &avail->tstamp);
+        /* Still need to return avail even if tstamp can't be filled in */
 
         /* FIXME: This needs to be different for capture stream,
            available is # of compressed data, for playback it's
@@ -517,11 +520,14 @@ out:
 static inline int
 snd_compr_tstamp(struct snd_compr_stream *stream, unsigned long arg)
 {
-        struct snd_compr_tstamp tstamp;
+        struct snd_compr_tstamp tstamp = {0};
+        int ret;
 
-        snd_compr_update_tstamp(stream, &tstamp);
-        return copy_to_user((struct snd_compr_tstamp __user *)arg,
-                &tstamp, sizeof(tstamp)) ? -EFAULT : 0;
+        ret = snd_compr_update_tstamp(stream, &tstamp);
+        if (ret == 0)
+                ret = copy_to_user((struct snd_compr_tstamp __user *)arg,
+                        &tstamp, sizeof(tstamp)) ? -EFAULT : 0;
+        return ret;
 }
 
 static int snd_compr_pause(struct snd_compr_stream *stream)