msghdr is allocated on the stack at recv_prep, which means it may go out
of scope before the kernel has a chance to complete the operation.  This
results in spurious test failures when we reach far enough into recv_fn
to reuse the stack space before op_recvmsg executes.  I found it easily
reproducible when compiling with '-O0 -g3' to avoid gcc from optimizing
further local variables out of the stack.

Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
---
 test/send_recvmsg.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/test/send_recvmsg.c b/test/send_recvmsg.c
index f2e1efc0..9154b6c0 100644
--- a/test/send_recvmsg.c
+++ b/test/send_recvmsg.c
@@ -32,10 +32,9 @@ static int ud;
 static int no_pbuf_ring;
 
 static int recv_prep(struct io_uring *ring, int *sockfd, struct iovec iov[],
-		     int iov_count, int bgid, int async)
+		     int iov_count, int bgid, int async, struct msghdr *msg)
 {
 	struct sockaddr_in saddr;
-	struct msghdr msg;
 	struct io_uring_sqe *sqe;
 	int ret, val = 1;
 
@@ -66,7 +65,7 @@ static int recv_prep(struct io_uring *ring, int *sockfd, struct iovec iov[],
 		return 1;
 	}
 
-	io_uring_prep_recvmsg(sqe, *sockfd, &msg, 0);
+	io_uring_prep_recvmsg(sqe, *sockfd, msg, 0);
 	if (bgid) {
 		iov->iov_base = NULL;
 		sqe->flags |= IOSQE_BUFFER_SELECT;
@@ -76,10 +75,10 @@ static int recv_prep(struct io_uring *ring, int *sockfd, struct iovec iov[],
 	sqe->user_data = ++ud;
 	if (async)
 		sqe->flags |= IOSQE_ASYNC;
-	memset(&msg, 0, sizeof(msg));
-	msg.msg_namelen = sizeof(struct sockaddr_in);
-	msg.msg_iov = iov;
-	msg.msg_iovlen = iov_count;
+	memset(msg, 0, sizeof(*msg));
+	msg->msg_namelen = sizeof(struct sockaddr_in);
+	msg->msg_iov = iov;
+	msg->msg_iovlen = iov_count;
 
 	ret = io_uring_submit(ring);
 	if (ret <= 0) {
@@ -168,6 +167,7 @@ static void *recv_fn(void *data)
 	struct io_uring_buf_ring *br = NULL;
 	char buf[MAX_MSG + 1];
 	struct iovec iov[MAX_IOV_COUNT];
+	struct msghdr msg;
 	struct io_uring ring;
 	int ret, sockfd;
 
@@ -225,7 +225,7 @@ static void *recv_fn(void *data)
 
 	ret = recv_prep(&ring, &sockfd, iov, rd->iov_count,
 			(rd->buf_ring || rd->buf_select) ? BUF_BGID : 0,
-			rd->async);
+			rd->async, &msg);
 	if (ret) {
 		fprintf(stderr, "recv_prep failed: %d\n", ret);
 		goto err;
-- 
2.54.0