Don't attempt to create a voice frame on a read error

Prior to this patch, a read error in snd_pcm_readi would still be treated as a
nominal result when constructing a voice frame from the expected data. Since
the value returned is negative, as opposed to the number of samples read,
this could result in a crash. With this patch, we now return a null frame
when a read error is detected.

Note that the patch on ASTERISK-21329 was modified slightly for this commit,
in that we bail immediately on detecting the read error, rather than bypassing
the construction of the voice frame.

(closes issue ASTERISK-21329)
Reported by: Keiichiro Kawasaki
patches:
  chan_alsa.diff uploaded by kawasaki (License 6489)
........

Merged revisions 385633 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 385634 from http://svn.asterisk.org/svn/asterisk/branches/11

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@385635 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/channels/chan_alsa.c b/channels/chan_alsa.c
index c43decb1c1b2140d36d790e9be9663e641c3f46d..7f54d6cfaecb089a0806805786b773d981067995 100644 (file)
--- a/channels/chan_alsa.c
+++ b/channels/chan_alsa.c
@@ -483,6 +483,13 @@ static struct ast_frame *alsa_read(struct ast_channel *chan)
        } else if (r < 0) {
                ast_log(LOG_ERROR, "Read error: %s\n", snd_strerror(r));
        }
+
+       /* Return NULL frame on error */
+       if (r < 0) {
+               ast_mutex_unlock(&alsalock);
+               return &f;
+       }
+
        /* Update positions */
        readpos += r;
        left -= r;