[PATCH 6.18.y v2 4/7] net/handshake: Fix null-ptr-deref in handshake_complete()

From: Wang Liang <[email protected]>

A null pointer dereference in handshake_complete() was observed [1].

When handshake_req_next() return NULL in handshake_nl_accept_doit(),
function handshake_complete() will be called unexpectedly which triggers
this crash. Fix it by goto out_status when req is NULL.

[1]
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] SMP KASAN PTI
RIP: 0010:handshake_complete+0x36/0x2b0 net/handshake/request.c:288
Call Trace:
 <TASK>
 handshake_nl_accept_doit+0x32d/0x7e0 net/handshake/netlink.c:129
 genl_family_rcv_msg_doit+0x204/0x300 net/netlink/genetlink.c:1115
 genl_family_rcv_msg+0x436/0x670 net/netlink/genetlink.c:1195
 genl_rcv_msg+0xcc/0x170 net/netlink/genetlink.c:1210
 netlink_rcv_skb+0x14c/0x430 net/netlink/af_netlink.c:2550
 genl_rcv+0x2d/0x40 net/netlink/genetlink.c:1219
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x878/0xb20 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x897/0xd70 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa39/0xbf0 net/socket.c:2592
 ___sys_sendmsg+0x121/0x1c0 net/socket.c:2646
 __sys_sendmsg+0x155/0x200 net/socket.c:2678
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x5f/0x350 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
 </TASK>

Fixes: fe67b063f687 ("net/handshake: convert handshake_nl_accept_doit() to FD_PREPARE()")
Reviewed-by: Chuck Lever <[email protected]>
Reported-by: Dan Carpenter <[email protected]>
Closes: https://lore.kernel.org/kernel-tls-handshake/[email protected]/T/#m7cfa5c11efc626d77622b2981591197a2acdd65e
Signed-off-by: Wang Liang <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

(cherry picked from commit dabac51b8102e1643d8e297a8e6948dab190aa4c)
Signed-off-by: Wentao Guan <[email protected]>
---
 net/handshake/netlink.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c
index 7b1d42607ae68..039344979de93 100644
--- a/net/handshake/netlink.c
+++ b/net/handshake/netlink.c
@@ -126,7 +126,8 @@ int handshake_nl_accept_doit(struct sk_buff *skb, struct genl_info *info)
 	}
 
 out_complete:
-	handshake_complete(req, -EIO, NULL);
+	if (req)
+		handshake_complete(req, -EIO, NULL);
 out_status:
 	trace_handshake_cmd_accept_err(net, req, NULL, err);
 	return err;
-- 
2.30.2