From fc1b7535cbc030f33dea820bece7a7283248566b Mon Sep 17 00:00:00 2001
From: Peilin Ye <yepeilin.cs@gmail.com>
Date: Thu, 30 Jul 2020 15:20:26 -0400
Subject: [PATCH 07/12] rds: Prevent kernel-infoleak in rds_notify_queue_get()
Git-commit: bbc8a99e952226c585ac17477a85ef1194501762
Patch-mainline: v5.8
References: git-fixes

rds_notify_queue_get() is potentially copying uninitialized kernel stack
memory to userspace since the compiler may leave a 4-byte hole at the end
of `cmsg`.

In 2016 we tried to fix this issue by doing `= { 0 };` on `cmsg`, which
unfortunately does not always initialize that 4-byte hole. Fix it by using
memset() instead.

Cc: stable@vger.kernel.org
Fixes: f037590fff30 ("rds: fix a leak of kernel memory")
Fixes: bdbe6fbc6a2f ("RDS: recv.c")
Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Denis Kirjanov <dkirjanov@suse.com>
---
 net/rds/recv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/rds/recv.c b/net/rds/recv.c
index 4aeeb5b6843f..e0c3b81ba3b6 100644
--- a/net/rds/recv.c
+++ b/net/rds/recv.c
@@ -446,12 +446,13 @@ static int rds_still_queued(struct rds_sock *rs, struct rds_incoming *inc,
 int rds_notify_queue_get(struct rds_sock *rs, struct msghdr *msghdr)
 {
 	struct rds_notifier *notifier;
-	struct rds_rdma_notify cmsg = { 0 }; /* fill holes with zero */
+	struct rds_rdma_notify cmsg;
 	unsigned int count = 0, max_messages = ~0U;
 	unsigned long flags;
 	LIST_HEAD(copy);
 	int err = 0;
 
+	memset(&cmsg, 0, sizeof(cmsg));	/* fill holes with zero */
 
 	/* put_cmsg copies to user space and thus may sleep. We can't do this
 	 * with rs_lock held, so first grab as many notifications as we can stuff
-- 
2.16.4