[PATCH net 1/2] bpf, sockmap: Avoid sk_prot reset on sockmap unlink with ULP set

[Dong Chenchen <dongchenchen2@huawei.com>]

WARNING: CPU: 0 PID: 6558 at net/core/sock_map.c:1703 sock_map_close+0x3c4/0x480
Modules linked in:
CPU: 0 UID: 0 PID: 6558 Comm: syz-executor.14 Not tainted 6.14.0-rc5+ #238
RIP: 0010:sock_map_close+0x3c4/0x480
Call Trace:
 <TASK>
 inet_release+0x144/0x280
 __sock_release+0xb8/0x270
 sock_close+0x1e/0x30
 __fput+0x3c6/0xb30
 __fput_sync+0x7b/0x90
 __x64_sys_close+0x90/0x120
 do_syscall_64+0x5d/0x170
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

The root cause is:
bpf_prog_attach(BPF_SK_SKB_STREAM_VERDICT)
tcp_set_ulp //set ulp after sockmap add
	icsk->icsk_ulp_ops = ulp_ops;
sock_hash_update_common
  sock_map_unref
    sock_map_del_link
      psock->psock_update_sk_prot(sk, psock, false);
	sk->sk_prot->close = sock_map_close
sk_psock_drop
  sk_psock_restore_proto
    tcp_bpf_update_proto
       tls_update //not redo sk_prot to tcp prot
inet_release
  sk->sk_prot->close
    sock_map_close
      WARN(sk->sk_prot->close == sock_map_close)

commit e34a07c0ae39 ("sock: redo the psock vs ULP protection check")
has moved ulp check from tcp_bpf_update_proto() to psock init.
If sk sets ulp after being added to sockmap, it will reset sk_prot to
BPF_BASE when removed from sockmap. After the psock is dropped, it will
not reset sk_prot back to the tcp prot, only tls context update is
performed. This can trigger a warning in sock_map_close() due to
recursion of sk->sk_prot->close.

To fix this issue, skip the sk_prot operations redo when deleting link
from sockmap if ULP is set.

Fixes: e34a07c0ae39 ("sock: redo the psock vs ULP protection check")
Fixes: c0d95d3380ee ("bpf, sockmap: Re-evaluate proto ops when psock is removed from sockmap")
Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com>
---
 net/core/sock_map.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 82a14f131d00..a3ed1f2cf8a2 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -170,7 +170,7 @@ static void sock_map_del_link(struct sock *sk,
 		if (verdict_stop)
 			sk_psock_stop_verdict(sk, psock);
 
-		if (psock->psock_update_sk_prot)
+		if (!(sk_is_inet(sk) && inet_csk_has_ulp(sk)) && psock->psock_update_sk_prot)
 			psock->psock_update_sk_prot(sk, psock, false);
 		write_unlock_bh(&sk->sk_callback_lock);
 	}
-- 
2.34.1