[PATCH 6.1 165/195] bpf, sockmap: Fix NULL pointer dereference in sk_psock_verdict_data_ready()

Greg Kroah-Hartman
2024-02-27T14:21:14Z

From: Shigeru Yoshida <syoshida@redhat.com>

[ 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@syzkaller.appspotmail.com
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: syzbot+fd7b34375c1c8ce29c93@syzkaller.appspotmail.com
Acked-by: John Fastabend <john.fastabend@gmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=fd7b34375c1c8ce29c93 [1]
Link: https://lore.kernel.org/bpf/20240218150933.6004-1-syoshida@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 3818035ea0021..39643f78cf782 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -1217,8 +1217,11 @@ 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