[LTP] [PATCH 1/2] msgrcv07: Check negative msg type filters

[Richard Palethorpe]

It should leave higher message types on the queue if they are above
the specified type's magnitude.

Also check what happens when MSG_EXCEPT is passed with a negative msg
type. This behavior is unspecified, but presently the kernel ignores
the flag if the type is negative. The motivation to check this is long
handling in 32bit compat mode. If the msg type is not sign extended
then it will be treated as a large positive integer. In this case we
should receive the remaining message.

On the current kernel under x86 the test passes because the system
call has an explicit compat variant which performs the sign
extension. Otherwise it would fail.

Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
---
 testcases/kernel/syscalls/ipc/msgrcv/msgrcv07.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/testcases/kernel/syscalls/ipc/msgrcv/msgrcv07.c b/testcases/kernel/syscalls/ipc/msgrcv/msgrcv07.c
index 2c687c5c8..8635ef7a4 100644
--- a/testcases/kernel/syscalls/ipc/msgrcv/msgrcv07.c
+++ b/testcases/kernel/syscalls/ipc/msgrcv/msgrcv07.c
@@ -232,6 +232,13 @@ static void test_negative_msgtyp(void)
 			"-msgtyp didn't get the first message in the queue with the lowest type");
 	}
 
+	TST_EXP_FAIL(msgrcv(queue_id, &rcv_buf, MSGSIZE, -MSGTYPE1, IPC_NOWAIT),
+		     ENOMSG,
+		     "-msgtype didn't recv next lowest msg");
+	TST_EXP_FAIL(msgrcv(queue_id, &rcv_buf, MSGSIZE, -MSGTYPE1, MSG_EXCEPT | IPC_NOWAIT),
+		     ENOMSG,
+		     "-msgtype (with except) didn't recv next lowest msg");
+
 exit:
 	SAFE_MSGCTL(queue_id, IPC_RMID, NULL);
 	queue_id = -1;
-- 
2.31.1