[PATCH 6.6 113/143] mptcp: fix possible deadlock in subflow diag

Greg Kroah-Hartman
2024-03-04T21:40:53Z

From: Paolo Abeni <pabeni@redhat.com>

commit d6a9608af9a75d13243d217f6ce1e30e57d56ffe upstream.

Syzbot and Eric reported a lockdep splat in the subflow diag:

WARNING: possible circular locking dependency detected
6.8.0-rc4-syzkaller-00212-g40b9385dd8e6 #0 Not tainted

syz-executor.2/24141 is trying to acquire lock:
ffff888045870130 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at:
tcp_diag_put_ulp net/ipv4/tcp_diag.c:100 [inline]
ffff888045870130 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at:
tcp_diag_get_aux+0x738/0x830 net/ipv4/tcp_diag.c:137

but task is already holding lock:
ffffc9000135e488 (&h->lhash2[i].lock){+.+.}-{2:2}, at: spin_lock
include/linux/spinlock.h:351 [inline]
ffffc9000135e488 (&h->lhash2[i].lock){+.+.}-{2:2}, at:
inet_diag_dump_icsk+0x39f/0x1f80 net/ipv4/inet_diag.c:1038

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&h->lhash2[i].lock){+.+.}-{2:2}:
lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
__inet_hash+0x335/0xbe0 net/ipv4/inet_hashtables.c:743
inet_csk_listen_start+0x23a/0x320 net/ipv4/inet_connection_sock.c:1261
__inet_listen_sk+0x2a2/0x770 net/ipv4/af_inet.c:217
inet_listen+0xa3/0x110 net/ipv4/af_inet.c:239
rds_tcp_listen_init+0x3fd/0x5a0 net/rds/tcp_listen.c:316
rds_tcp_init_net+0x141/0x320 net/rds/tcp.c:577
ops_init+0x352/0x610 net/core/net_namespace.c:136
__register_pernet_operations net/core/net_namespace.c:1214 [inline]
register_pernet_operations+0x2cb/0x660 net/core/net_namespace.c:1283
register_pernet_device+0x33/0x80 net/core/net_namespace.c:1370
rds_tcp_init+0x62/0xd0 net/rds/tcp.c:735
do_one_initcall+0x238/0x830 init/main.c:1236
do_initcall_level+0x157/0x210 init/main.c:1298
do_initcalls+0x3f/0x80 init/main.c:1314
kernel_init_freeable+0x42f/0x5d0 init/main.c:1551
kernel_init+0x1d/0x2a0 init/main.c:1441
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:242

-> #0 (k-sk_lock-AF_INET6){+.+.}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18ca/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1345/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754
lock_sock_fast include/net/sock.h:1723 [inline]
subflow_get_info+0x166/0xd20 net/mptcp/diag.c:28
tcp_diag_put_ulp net/ipv4/tcp_diag.c:100 [inline]
tcp_diag_get_aux+0x738/0x830 net/ipv4/tcp_diag.c:137
inet_sk_diag_fill+0x10ed/0x1e00 net/ipv4/inet_diag.c:345
inet_diag_dump_icsk+0x55b/0x1f80 net/ipv4/inet_diag.c:1061
__inet_diag_dump+0x211/0x3a0 net/ipv4/inet_diag.c:1263
inet_diag_dump_compat+0x1c1/0x2d0 net/ipv4/inet_diag.c:1371
netlink_dump+0x59b/0xc80 net/netlink/af_netlink.c:2264
__netlink_dump_start+0x5df/0x790 net/netlink/af_netlink.c:2370
netlink_dump_start include/linux/netlink.h:338 [inline]
inet_diag_rcv_msg_compat+0x209/0x4c0 net/ipv4/inet_diag.c:1405
sock_diag_rcv_msg+0xe7/0x410
netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2543
sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:280
netlink_unicast_kernel net/netlink/af_netlink.c:1341 [inline]
netlink_unicast+0x7ea/0x980 net/netlink/af_netlink.c:1367
netlink_sendmsg+0xa3b/0xd70 net/netlink/af_netlink.c:1908
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

As noted by Eric we can break the lock dependency chain avoid
dumping any extended info for the mptcp subflow listener:
nothing actually useful is presented there.

Fixes: b8adb69a7d29 ("mptcp: fix lockless access in subflow ULP diag")
Cc: stable@vger.kernel.org
Reported-by: Eric Dumazet <edumazet@google.com>
Closes: https://lore.kernel.org/netdev/CANn89iJ=Oecw6OZDwmSYc9HJKQ_G32uN11L+oUcMu+TOD5Xiaw@mail.gmail.com/
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240223-upstream-net-20240223-misc-fixes-v1-9-162e87e48497@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/mptcp/diag.c | 3 +++
1 file changed, 3 insertions(+)

--- a/net/mptcp/diag.c
+++ b/net/mptcp/diag.c
@@ -21,6 +21,9 @@ static int subflow_get_info(struct sock
bool slow;
int err;

+ if (inet_sk_state_load(sk) == TCP_LISTEN)
+ return 0;
+
start = nla_nest_start_noflag(skb, INET_ULP_INFO_MPTCP);
if (!start)
return -EMSGSIZE;