Patch "bpf, skmsg: Fix NULL pointer dereference in sk_psock_skb_ingress_enqueue" has been added to the 6.8-stable tree

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This is a note to let you know that I've just added the patch titled

    bpf, skmsg: Fix NULL pointer dereference in sk_psock_skb_ingress_enqueue

to the 6.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bpf-skmsg-fix-null-pointer-dereference-in-sk_psock_s.patch
and it can be found in the queue-6.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 38bb114ffd565752815164f04b5eea8b3a19d8eb
Author: Jason Xing <kernelxing@xxxxxxxxxxx>
Date:   Thu Apr 4 10:10:01 2024 +0800

    bpf, skmsg: Fix NULL pointer dereference in sk_psock_skb_ingress_enqueue
    
    [ Upstream commit 6648e613226e18897231ab5e42ffc29e63fa3365 ]
    
    Fix NULL pointer data-races in sk_psock_skb_ingress_enqueue() which
    syzbot reported [1].
    
    [1]
    BUG: KCSAN: data-race in sk_psock_drop / sk_psock_skb_ingress_enqueue
    
    write to 0xffff88814b3278b8 of 8 bytes by task 10724 on cpu 1:
     sk_psock_stop_verdict net/core/skmsg.c:1257 [inline]
     sk_psock_drop+0x13e/0x1f0 net/core/skmsg.c:843
     sk_psock_put include/linux/skmsg.h:459 [inline]
     sock_map_close+0x1a7/0x260 net/core/sock_map.c:1648
     unix_release+0x4b/0x80 net/unix/af_unix.c:1048
     __sock_release net/socket.c:659 [inline]
     sock_close+0x68/0x150 net/socket.c:1421
     __fput+0x2c1/0x660 fs/file_table.c:422
     __fput_sync+0x44/0x60 fs/file_table.c:507
     __do_sys_close fs/open.c:1556 [inline]
     __se_sys_close+0x101/0x1b0 fs/open.c:1541
     __x64_sys_close+0x1f/0x30 fs/open.c:1541
     do_syscall_64+0xd3/0x1d0
     entry_SYSCALL_64_after_hwframe+0x6d/0x75
    
    read to 0xffff88814b3278b8 of 8 bytes by task 10713 on cpu 0:
     sk_psock_data_ready include/linux/skmsg.h:464 [inline]
     sk_psock_skb_ingress_enqueue+0x32d/0x390 net/core/skmsg.c:555
     sk_psock_skb_ingress_self+0x185/0x1e0 net/core/skmsg.c:606
     sk_psock_verdict_apply net/core/skmsg.c:1008 [inline]
     sk_psock_verdict_recv+0x3e4/0x4a0 net/core/skmsg.c:1202
     unix_read_skb net/unix/af_unix.c:2546 [inline]
     unix_stream_read_skb+0x9e/0xf0 net/unix/af_unix.c:2682
     sk_psock_verdict_data_ready+0x77/0x220 net/core/skmsg.c:1223
     unix_stream_sendmsg+0x527/0x860 net/unix/af_unix.c:2339
     sock_sendmsg_nosec net/socket.c:730 [inline]
     __sock_sendmsg+0x140/0x180 net/socket.c:745
     ____sys_sendmsg+0x312/0x410 net/socket.c:2584
     ___sys_sendmsg net/socket.c:2638 [inline]
     __sys_sendmsg+0x1e9/0x280 net/socket.c:2667
     __do_sys_sendmsg net/socket.c:2676 [inline]
     __se_sys_sendmsg net/socket.c:2674 [inline]
     __x64_sys_sendmsg+0x46/0x50 net/socket.c:2674
     do_syscall_64+0xd3/0x1d0
     entry_SYSCALL_64_after_hwframe+0x6d/0x75
    
    value changed: 0xffffffff83d7feb0 -> 0x0000000000000000
    
    Reported by Kernel Concurrency Sanitizer on:
    CPU: 0 PID: 10713 Comm: syz-executor.4 Tainted: G        W          6.8.0-syzkaller-08951-gfe46a7dd189e #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
    
    Prior to this, commit 4cd12c6065df ("bpf, sockmap: Fix NULL pointer
    dereference in sk_psock_verdict_data_ready()") fixed one NULL pointer
    similarly due to no protection of saved_data_ready. Here is another
    different caller causing the same issue because of the same reason. So
    we should protect it with sk_callback_lock read lock because the writer
    side in the sk_psock_drop() uses "write_lock_bh(&sk->sk_callback_lock);".
    
    To avoid errors that could happen in future, I move those two pairs of
    lock into the sk_psock_data_ready(), which is suggested by John Fastabend.
    
    Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
    Reported-by: syzbot+aa8c8ec2538929f18f2d@xxxxxxxxxxxxxxxxxxxxxxxxx
    Signed-off-by: Jason Xing <kernelxing@xxxxxxxxxxx>
    Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
    Reviewed-by: John Fastabend <john.fastabend@xxxxxxxxx>
    Closes: https://syzkaller.appspot.com/bug?extid=aa8c8ec2538929f18f2d
    Link: https://lore.kernel.org/all/20240329134037.92124-1-kerneljasonxing@xxxxxxxxx
    Link: https://lore.kernel.org/bpf/20240404021001.94815-1-kerneljasonxing@xxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index e65ec3fd27998..a509caf823d61 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -461,10 +461,12 @@ static inline void sk_psock_put(struct sock *sk, struct sk_psock *psock)
 
 static inline void sk_psock_data_ready(struct sock *sk, struct sk_psock *psock)
 {
+	read_lock_bh(&sk->sk_callback_lock);
 	if (psock->saved_data_ready)
 		psock->saved_data_ready(sk);
 	else
 		sk->sk_data_ready(sk);
+	read_unlock_bh(&sk->sk_callback_lock);
 }
 
 static inline void psock_set_prog(struct bpf_prog **pprog,
diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 4d75ef9d24bfa..fd20aae30be23 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -1226,11 +1226,8 @@ static void sk_psock_verdict_data_ready(struct sock *sk)
 
 		rcu_read_lock();
 		psock = sk_psock(sk);
-		if (psock) {
-			read_lock_bh(&sk->sk_callback_lock);
+		if (psock)
 			sk_psock_data_ready(sk, psock);
-			read_unlock_bh(&sk->sk_callback_lock);
-		}
 		rcu_read_unlock();
 	}
 }




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