linux-kernel - [PATCH] net/socket: Ensure length of input socket option param >= sizeof(int)

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Date: Tue,  9 Apr 2024 20:15:53 +0800
From: Edward Adam Davis <eadavis@...com>
To: pmenzel@...gen.mpg.de
Cc: netdev@...r.kernel.org,
	eadavis@...com,
	johan.hedberg@...il.com,
	linux-bluetooth@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	luiz.dentz@...il.com,
	marcel@...tmann.org,
	syzbot+d4ecae01a53fd9b42e7d@...kaller.appspotmail.com,
	syzkaller-bugs@...glegroups.com
Subject: [PATCH] net/socket: Ensure length of input socket option param >= sizeof(int)

The optlen value passed by syzbot to _sys_setsockopt() is 2, which results in
only 2 bytes being allocated when allocating memory to kernel_optval, and the
optval size passed when calling the function copy_from_sockptr() is 4 bytes.
Here, optlen is determined uniformly in the entry function __sys_setsockopt(). 
If its value is less than 4, the parameter is considered invalid.

Reported-by: syzbot+837ba09d9db969068367@...kaller.appspotmail.com
Reported-by: syzbot+b71011ec0a23f4d15625@...kaller.appspotmail.com
Reported-by: syzbot+d4ecae01a53fd9b42e7d@...kaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
 net/socket.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/socket.c b/net/socket.c
index e5f3af49a8b6..ac8fd4f6ebfe 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2327,6 +2327,9 @@ int __sys_setsockopt(int fd, int level, int optname, char __user *user_optval,
 	int err, fput_needed;
 	struct socket *sock;
 
+	if (optlen < sizeof(int))
+		return -EINVAL;
+
 	sock = sockfd_lookup_light(fd, &err, &fput_needed);
 	if (!sock)
 		return err;
-- 
2.43.0