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9ca5e7ecab
When a file descriptor of pppol2tp socket is passed as file descriptor
of UDP socket, a recursive deadlock occurs in l2tp_tunnel_register().
This situation is reproduced by the following program:
int main(void)
{
int sock;
struct sockaddr_pppol2tp addr;
sock = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OL2TP);
if (sock < 0) {
perror("socket");
return 1;
}
addr.sa_family = AF_PPPOX;
addr.sa_protocol = PX_PROTO_OL2TP;
addr.pppol2tp.pid = 0;
addr.pppol2tp.fd = sock;
addr.pppol2tp.addr.sin_family = PF_INET;
addr.pppol2tp.addr.sin_port = htons(0);
addr.pppol2tp.addr.sin_addr.s_addr = inet_addr("192.168.0.1");
addr.pppol2tp.s_tunnel = 1;
addr.pppol2tp.s_session = 0;
addr.pppol2tp.d_tunnel = 0;
addr.pppol2tp.d_session = 0;
if (connect(sock, (const struct sockaddr *)&addr, sizeof(addr)) < 0) {
perror("connect");
return 1;
}
return 0;
}
This program causes the following lockdep warning:
============================================
WARNING: possible recursive locking detected
6.2.0-rc5-00205-gc96618275234 #56 Not tainted
--------------------------------------------
repro/8607 is trying to acquire lock:
ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: l2tp_tunnel_register+0x2b7/0x11c0
but task is already holding lock:
ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0xa82/0x1a30
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(sk_lock-AF_PPPOX);
lock(sk_lock-AF_PPPOX);
*** DEADLOCK ***
May be due to missing lock nesting notation
1 lock held by repro/8607:
#0: ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0xa82/0x1a30
stack backtrace:
CPU: 0 PID: 8607 Comm: repro Not tainted 6.2.0-rc5-00205-gc96618275234 #56
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x100/0x178
__lock_acquire.cold+0x119/0x3b9
? lockdep_hardirqs_on_prepare+0x410/0x410
lock_acquire+0x1e0/0x610
? l2tp_tunnel_register+0x2b7/0x11c0
? lock_downgrade+0x710/0x710
? __fget_files+0x283/0x3e0
lock_sock_nested+0x3a/0xf0
? l2tp_tunnel_register+0x2b7/0x11c0
l2tp_tunnel_register+0x2b7/0x11c0
? sprintf+0xc4/0x100
? l2tp_tunnel_del_work+0x6b0/0x6b0
? debug_object_deactivate+0x320/0x320
? lockdep_init_map_type+0x16d/0x7a0
? lockdep_init_map_type+0x16d/0x7a0
? l2tp_tunnel_create+0x2bf/0x4b0
? l2tp_tunnel_create+0x3c6/0x4b0
pppol2tp_connect+0x14e1/0x1a30
? pppol2tp_put_sk+0xd0/0xd0
? aa_sk_perm+0x2b7/0xa80
? aa_af_perm+0x260/0x260
? bpf_lsm_socket_connect+0x9/0x10
? pppol2tp_put_sk+0xd0/0xd0
__sys_connect_file+0x14f/0x190
__sys_connect+0x133/0x160
? __sys_connect_file+0x190/0x190
? lockdep_hardirqs_on+0x7d/0x100
? ktime_get_coarse_real_ts64+0x1b7/0x200
? ktime_get_coarse_real_ts64+0x147/0x200
? __audit_syscall_entry+0x396/0x500
__x64_sys_connect+0x72/0xb0
do_syscall_64+0x38/0xb0
entry_SYSCALL_64_after_hwframe+0x63/0xcd
This patch fixes the issue by getting/creating the tunnel before
locking the pppol2tp socket.
Fixes:
|
||
|---|---|---|
| .. | ||
| 6lowpan | ||
| 9p | ||
| 802 | ||
| 8021q | ||
| appletalk | ||
| atm | ||
| ax25 | ||
| batman-adv | ||
| bluetooth | ||
| bpf | ||
| bpfilter | ||
| bridge | ||
| caif | ||
| can | ||
| ceph | ||
| core | ||
| dcb | ||
| dccp | ||
| dns_resolver | ||
| dsa | ||
| ethernet | ||
| ethtool | ||
| hsr | ||
| ieee802154 | ||
| ife | ||
| ipv4 | ||
| ipv6 | ||
| iucv | ||
| kcm | ||
| key | ||
| l2tp | ||
| l3mdev | ||
| lapb | ||
| llc | ||
| mac80211 | ||
| mac802154 | ||
| mctp | ||
| mpls | ||
| mptcp | ||
| ncsi | ||
| netfilter | ||
| netlabel | ||
| netlink | ||
| netrom | ||
| nfc | ||
| nsh | ||
| openvswitch | ||
| packet | ||
| phonet | ||
| psample | ||
| qrtr | ||
| rds | ||
| rfkill | ||
| rose | ||
| rxrpc | ||
| sched | ||
| sctp | ||
| smc | ||
| strparser | ||
| sunrpc | ||
| switchdev | ||
| tipc | ||
| tls | ||
| unix | ||
| vmw_vsock | ||
| wireless | ||
| x25 | ||
| xdp | ||
| xfrm | ||
| compat.c | ||
| devres.c | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||
| socket.c | ||
| sysctl_net.c | ||