[PATCH 6.7 300/334] bpf, sockmap: Fix NULL pointer dereference in sk_psock_verdict_data_ready()

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6.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Shigeru Yoshida <syoshida@xxxxxxxxxx>

[ Upstream commit 4cd12c6065dfcdeba10f49949bffcf383b3952d8 ]

syzbot reported the following NULL pointer dereference issue [1]:

  BUG: kernel NULL pointer dereference, address: 0000000000000000
  [...]
  RIP: 0010:0x0
  [...]
  Call Trace:
   <TASK>
   sk_psock_verdict_data_ready+0x232/0x340 net/core/skmsg.c:1230
   unix_stream_sendmsg+0x9b4/0x1230 net/unix/af_unix.c:2293
   sock_sendmsg_nosec net/socket.c:730 [inline]
   __sock_sendmsg+0x221/0x270 net/socket.c:745
   ____sys_sendmsg+0x525/0x7d0 net/socket.c:2584
   ___sys_sendmsg net/socket.c:2638 [inline]
   __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2667
   do_syscall_64+0xf9/0x240
   entry_SYSCALL_64_after_hwframe+0x6f/0x77

If sk_psock_verdict_data_ready() and sk_psock_stop_verdict() are called
concurrently, psock->saved_data_ready can be NULL, causing the above issue.

This patch fixes this issue by calling the appropriate data ready function
using the sk_psock_data_ready() helper and protecting it from concurrency
with sk->sk_callback_lock.

Fixes: 6df7f764cd3c ("bpf, sockmap: Wake up polling after data copy")
Reported-by: syzbot+fd7b34375c1c8ce29c93@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Shigeru Yoshida <syoshida@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Tested-by: syzbot+fd7b34375c1c8ce29c93@xxxxxxxxxxxxxxxxxxxxxxxxx
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
Closes: https://syzkaller.appspot.com/bug?extid=fd7b34375c1c8ce29c93 [1]
Link: https://lore.kernel.org/bpf/20240218150933.6004-1-syoshida@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/core/skmsg.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 93ecfceac1bc4..4d75ef9d24bfa 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -1226,8 +1226,11 @@ static void sk_psock_verdict_data_ready(struct sock *sk)
 
 		rcu_read_lock();
 		psock = sk_psock(sk);
-		if (psock)
-			psock->saved_data_ready(sk);
+		if (psock) {
+			read_lock_bh(&sk->sk_callback_lock);
+			sk_psock_data_ready(sk, psock);
+			read_unlock_bh(&sk->sk_callback_lock);
+		}
 		rcu_read_unlock();
 	}
 }
-- 
2.43.0







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