Ack,
Pavel
On Thu, 2017-03-16 at 16:10 +0100, Christophe Fergeau wrote:
> 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);
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