[PATCH 04/23] Fix null dereference in socket_recv_thread()

[Valerie Aurora]

From: Chris Kirby <ckirby at versity.com>

In socket_recv_thread(), don't try to iov_append() a NULL buffer.
Compiler optimizations hide this bug for some versions of gcc.

Signed-off-by: Chris Kirby <ckirby at versity.com>
---
 shared/mtr-socket.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/shared/mtr-socket.c b/shared/mtr-socket.c
index 3794c0f..db8221a 100644
--- a/shared/mtr-socket.c
+++ b/shared/mtr-socket.c
@@ -212,7 +212,9 @@ static void socket_recv_thread(struct thread *thr, void *arg)
 		}
 
 		iovcnt = iov_append(iov, 0, page_address(ctl_page), mdesc.ctl_size);
-		iovcnt = iov_append(iov, iovcnt, page_address(mdesc.data_page), mdesc.data_size);
+
+		if (mdesc.data_size)
+			iovcnt = iov_append(iov, iovcnt, page_address(mdesc.data_page), mdesc.data_size);
 
 		ret = whole_iovec(readv, pinf->fd, iov, iovcnt);
 		if (ret < 0)
-- 
2.48.1