On my 64 bit Fedora 25, CMSG_SPACE() adds 4 bytes of padding after the
file descriptor in the control data. This causes warnings when ran under
valgrind as we set msg_controllen to CMSG_SPACE().
This commit fills the control data to 0 to avoid these warnings.
==30301== Syscall param sendmsg(msg.msg_control) points to uninitialised byte(s)
==30301== at 0x8127367: sendmsg (sendmsg.c:28)
==30301== by 0x41880B: reds_stream_send_msgfd (reds-stream.c:295)
==30301== by 0x40953F: main (test-stream.c:121)
==30301== Address 0xffefff1b4 is on thread 1's stack
==30301== in frame #1, created by reds_stream_send_msgfd (reds-stream.c:263)
---
server/reds-stream.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/server/reds-stream.c b/server/reds-stream.c
index a813a8b..8ac296d 100644
--- a/server/reds-stream.c
+++ b/server/reds-stream.c
@@ -283,6 +283,10 @@ int reds_stream_send_msgfd(RedsStream *stream, int fd)
if (fd != -1) {
msgh.msg_control = control.data;
msgh.msg_controllen = sizeof(control.data);
+ /* CMSG_SPACE() might be larger than CMSG_LEN() as it can include some
+ * padding. We set the whole control data to 0 to avoid valgrind warnings
+ */
+ memset(control.data, 0, sizeof(control.data));
cmsg = CMSG_FIRSTHDR(&msgh);
cmsg->cmsg_len = CMSG_LEN(fd_size);
--
2.9.3
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