ipmi: Fix handling of messages with provided receive message pointer

commit e2c69490dda5d4c9f1bfbb2898989c8f3530e354 upstream.

Prior to commit b52da4054ee0 ("ipmi: Rework user message limit handling"),
i_ipmi_request() used to increase the user reference counter if the receive
message is provided by the caller of IPMI API functions. This is no longer
the case. However, ipmi_free_recv_msg() is still called and decreases the
reference counter. This results in the reference counter reaching zero,
the user data pointer is released, and all kinds of interesting crashes are
seen.

Fix the problem by increasing user reference counter if the receive message
has been provided by the caller.

Fixes: b52da4054ee0 ("ipmi: Rework user message limit handling")
Reported-by: Eric Dumazet <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Greg Thelen <[email protected]>
Signed-off-by: Guenter Roeck <[email protected]>
Message-ID: <[email protected]>
Signed-off-by: Corey Minyard <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: groeck

drivers/char/ipmi/ipmi_msghandler.c

@@ -2280,8 +2280,11 @@ static int i_ipmi_request(struct ipmi_user     *user,
 	if (supplied_recv) {
 		recv_msg = supplied_recv;
 		recv_msg->user = user;
-		if (user)
+		if (user) {
 			atomic_inc(&user->nr_msgs);
+			/* The put happens when the message is freed. */
+			kref_get(&user->refcount);
+		}
 	} else {
 		recv_msg = ipmi_alloc_recv_msg(user);
 		if (IS_ERR(recv_msg))