tcp: Fix refcnt handling in __inet_hash_connect().
syzbot reported a warning in sk_nulls_del_node_init_rcu().
The commit
66b60b0c8c4a ("dccp/tcp: Unhash sk from ehash for tb2 alloc
failure after check_estalblished().") tried to fix an issue that an
unconnected socket occupies an ehash entry when bhash2 allocation fails.
In such a case, we need to revert changes done by check_established(),
which does not hold refcnt when inserting socket into ehash.
So, to revert the change, we need to __sk_nulls_add_node_rcu() instead
of sk_nulls_add_node_rcu().
Otherwise, sock_put() will cause refcnt underflow and leak the socket.
[0]:
WARNING: CPU: 0 PID: 23948 at include/net/sock.h:799 sk_nulls_del_node_init_rcu+0x166/0x1a0 include/net/sock.h:799
Modules linked in:
CPU: 0 PID: 23948 Comm: syz-executor.2 Not tainted
6.8.0-rc6-syzkaller-00159-gc055fc00c07b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
RIP: 0010:sk_nulls_del_node_init_rcu+0x166/0x1a0 include/net/sock.h:799
Code: e8 7f 71 c6 f7 83 fb 02 7c 25 e8 35 6d c6 f7 4d 85 f6 0f 95 c0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc e8 1b 6d c6 f7 90 <0f> 0b 90 eb b2 e8 10 6d c6 f7 4c 89 e7 be 04 00 00 00 e8 63 e7 d2
RSP: 0018:
ffffc900032d7848 EFLAGS:
00010246
RAX:
ffffffff89cd0035 RBX:
0000000000000001 RCX:
0000000000040000
RDX:
ffffc90004de1000 RSI:
000000000003ffff RDI:
0000000000040000
RBP:
1ffff1100439ac26 R08:
ffffffff89ccffe3 R09:
1ffff1100439ac28
R10:
dffffc0000000000 R11:
ffffed100439ac29 R12:
ffff888021cd6140
R13:
dffffc0000000000 R14:
ffff88802a9bf5c0 R15:
ffff888021cd6130
FS:
00007f3b823f16c0(0000) GS:
ffff8880b9400000(0000) knlGS:
0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
CR2:
00007f3b823f0ff8 CR3:
000000004674a000 CR4:
00000000003506f0
DR0:
0000000000000000 DR1:
0000000000000000 DR2:
0000000000000000
DR3:
0000000000000000 DR6:
00000000fffe0ff0 DR7:
0000000000000400
Call Trace:
<TASK>
__inet_hash_connect+0x140f/0x20b0 net/ipv4/inet_hashtables.c:1139
dccp_v6_connect+0xcb9/0x1480 net/dccp/ipv6.c:956
__inet_stream_connect+0x262/0xf30 net/ipv4/af_inet.c:678
inet_stream_connect+0x65/0xa0 net/ipv4/af_inet.c:749
__sys_connect_file net/socket.c:2048 [inline]
__sys_connect+0x2df/0x310 net/socket.c:2065
__do_sys_connect net/socket.c:2075 [inline]
__se_sys_connect net/socket.c:2072 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:2072
do_syscall_64+0xf9/0x240
entry_SYSCALL_64_after_hwframe+0x6f/0x77
RIP: 0033:0x7f3b8167dda9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:
00007f3b823f10c8 EFLAGS:
00000246 ORIG_RAX:
000000000000002a
RAX:
ffffffffffffffda RBX:
00007f3b817abf80 RCX:
00007f3b8167dda9
RDX:
000000000000001c RSI:
0000000020000040 RDI:
0000000000000003
RBP:
00007f3b823f1120 R08:
0000000000000000 R09:
0000000000000000
R10:
0000000000000000 R11:
0000000000000246 R12:
0000000000000001
R13:
000000000000000b R14:
00007f3b817abf80 R15:
00007ffd3beb57b8
</TASK>
Reported-by: syzbot+12c506c1aae251e70449@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=12c506c1aae251e70449
Fixes: 66b60b0c8c4a ("dccp/tcp: Unhash sk from ehash for tb2 alloc failure after check_estalblished().")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240308201623.65448-1-kuniyu@amazon.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>