linux-kernel - Re: [syzbot] [net?] [nfc?] KASAN: slab-use-after-free Read in nfc_alloc_send

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Message-ID: <7d56a505-3093-4863-a7b1-9454ec6447ae@siddh.me>
Date:   Mon, 13 Nov 2023 18:13:46 +0530
From:   Siddh Raman Pant <code@...dh.me>
To:     syzbot+bbe84a4010eeea00982d@...kaller.appspotmail.com
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] [nfc?] KASAN: slab-use-after-free Read in
 nfc_alloc_send_skb

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

diff --git a/net/nfc/llcp_sock.c b/net/nfc/llcp_sock.c
index 645677f84dba..ea0e6c85866d 100644
--- a/net/nfc/llcp_sock.c                                                                 
+++ b/net/nfc/llcp_sock.c
@@ -796,6 +796,11 @@ static int llcp_sock_sendmsg(struct socket *sock, struct msghdr *msg,
        }                               
                                                 
        if (sk->sk_type == SOCK_DGRAM) { 
+               if (sk->sk_state != LLCP_BOUND) {
+                       release_sock(sk);
+                       return -ENOLINK;
+               }                                                 
+                                               
                DECLARE_SOCKADDR(struct sockaddr_nfc_llcp *, addr,
                                 msg->msg_name);