[PATCH 6.1 041/236] bpf, skmsg: Fix NULL pointer dereference in sk_psock_skb_ingress_enqueue

Greg Kroah-Hartman
2024-05-14T11:29:22Z

From: Jason Xing <kernelxing@tencent.com>

[ 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@syzkaller.appspotmail.com
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=aa8c8ec2538929f18f2d
Link: https://lore.kernel.org/all/20240329134037.92124-1-kerneljasonxing@gmail.com
Link: https://lore.kernel.org/bpf/20240404021001.94815-1-kerneljasonxing@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/skmsg.h | 2 ++
net/core/skmsg.c | 5 +----
2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index bd4418377bacf..062fe440f5d09 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -456,10 +456,12 @@ 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 39643f78cf782..8b0459a6b629f 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -1217,11 +1217,8 @@ 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();
}
}
--
2.43.0