Don't read past end of input when calling write()

int blah = 1;
...
write(chan->alertpipe[1], &blah, new_frames * sizeof(blah)) !=
(new_frames * sizeof(blah)))

is only valid when new_frames == 1. Otherwise we start reading into adjacent
variables declared on the stack. The read end discards what is read, so the
values don't matter but it's not a good idea to read past where we want even
though new_frames is almost always 1 and should never be large. This patch is
basically taken out of kpfleming's eventfd branch, as he mentioned that he
remembered fixing it there when I talked to him about this issue.

Review: https://reviewboard.asterisk.org/r/1583/

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@345163 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/main/channel.c b/main/channel.c
index 8b9473f56ccb57442c5c479475ed841cb7f6bd68..4499be8ed7c710790d9c397cefd70ddbe7173d70 100644 (file)
--- a/main/channel.c
+++ b/main/channel.c
@@ -1400,7 +1400,6 @@ static int __ast_queue_frame(struct ast_channel *chan, struct ast_frame *fin, in
 {
        struct ast_frame *f;
        struct ast_frame *cur;
-       int blah = 1;
        unsigned int new_frames = 0;
        unsigned int new_voice_frames = 0;
        unsigned int queued_frames = 0;
@@ -1499,7 +1498,10 @@ static int __ast_queue_frame(struct ast_channel *chan, struct ast_frame *fin, in
        }
 
        if (chan->alertpipe[1] > -1) {
-               if (write(chan->alertpipe[1], &blah, new_frames * sizeof(blah)) != (new_frames * sizeof(blah))) {
+               int blah[new_frames];
+
+               memset(blah, 1, sizeof(blah));
+               if (write(chan->alertpipe[1], &blah, sizeof(blah)) != (sizeof(blah))) {
                        ast_log(LOG_WARNING, "Unable to write to alert pipe on %s (qlen = %d): %s!\n",
                                chan->name, queued_frames, strerror(errno));
                }