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-and-tested-by: syzbot+fd7b34375c1c8ce29c93@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=fd7b34375c1c8ce29c93 [1]
Signed-off-by: Shigeru Yoshida <syoshida@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 93ecfceac1bc..4d75ef9d24bf 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
