net/dccp: dccp_create_openreq_child freed held lock

[Dmitry Vyukov]

Hello,

I've got the following report while running syzkaller fuzzer on
86292b33d4b79ee03e2f43ea0381ef85f077c760:

[ BUG: held lock freed! ]
4.10.0+ #234 Not tainted
-------------------------
syz-executor6/6898 is freeing memory
ffff88006286cac0-ffff88006286d3b7, with a lock still held there!
(slock-AF_INET6){+.-...}, at: [<ffffffff8362c2c9>] spin_lock
include/linux/spinlock.h:299 [inline]
(slock-AF_INET6){+.-...}, at: [<ffffffff8362c2c9>]
sk_clone_lock+0x3d9/0x12c0 net/core/sock.c:1504
5 locks held by syz-executor6/6898:
#0: (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff839a34b4>] lock_sock
include/net/sock.h:1460 [inline]
#0: (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff839a34b4>]
inet_stream_connect+0x44/0xa0 net/ipv4/af_inet.c:681
#1: (rcu_read_lock){......}, at: [<ffffffff83bc1c2a>]
inet6_csk_xmit+0x12a/0x5d0 net/ipv6/inet6_connection_sock.c:126
#2: (rcu_read_lock){......}, at: [<ffffffff8369b424>] __skb_unlink
include/linux/skbuff.h:1767 [inline]
#2: (rcu_read_lock){......}, at: [<ffffffff8369b424>] __skb_dequeue
include/linux/skbuff.h:1783 [inline]
#2: (rcu_read_lock){......}, at: [<ffffffff8369b424>]
process_backlog+0x264/0x730 net/core/dev.c:4835
#3: (rcu_read_lock){......}, at: [<ffffffff83aeb5c0>]
ip6_input_finish+0x0/0x1700 net/ipv6/ip6_input.c:59
#4: (slock-AF_INET6){+.-...}, at: [<ffffffff8362c2c9>] spin_lock
include/linux/spinlock.h:299 [inline]
#4: (slock-AF_INET6){+.-...}, at: [<ffffffff8362c2c9>]
sk_clone_lock+0x3d9/0x12c0 net/core/sock.c:1504

stack backtrace:
CPU: 3 PID: 6898 Comm: syz-executor6 Not tainted 4.10.0+ #234
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:15 [inline]
dump_stack+0x2ee/0x3ef lib/dump_stack.c:51
print_freed_lock_bug kernel/locking/lockdep.c:4248 [inline]
debug_check_no_locks_freed+0x4d2/0x5c0 kernel/locking/lockdep.c:4281
9pnet_virtio: no channels available for device ./bus
kmem_cache_free+0x62/0x240 mm/slab.c:3770
sk_prot_free net/core/sock.c:1375 [inline]
__sk_destruct+0x487/0x6b0 net/core/sock.c:1450
sk_destruct+0x47/0x80 net/core/sock.c:1458
__sk_free+0x57/0x230 net/core/sock.c:1466
sk_free+0x23/0x30 net/core/sock.c:1477
dccp_create_openreq_child+0x50e/0x610 net/dccp/minisocks.c:125
dccp_v6_request_recv_sock+0x1f1/0x17e0 net/dccp/ipv6.c:457
dccp_check_req+0x335/0x5a0 net/dccp/minisocks.c:186
dccp_v6_rcv+0x653/0x1d10 net/dccp/ipv6.c:711
ip6_input_finish+0x45b/0x1700 net/ipv6/ip6_input.c:279
NF_HOOK include/linux/netfilter.h:257 [inline]
ip6_input+0xdb/0x580 net/ipv6/ip6_input.c:322
dst_input include/net/dst.h:492 [inline]
ip6_rcv_finish+0x194/0x720 net/ipv6/ip6_input.c:69
NF_HOOK include/linux/netfilter.h:257 [inline]
ipv6_rcv+0x12df/0x2380 net/ipv6/ip6_input.c:203
__netif_receive_skb_core+0x1ac8/0x33f0 net/core/dev.c:4179
__netif_receive_skb+0x2a/0x170 net/core/dev.c:4217
process_backlog+0x11e/0x730 net/core/dev.c:4837
napi_poll net/core/dev.c:5171 [inline]
net_rx_action+0xeb4/0x1580 net/core/dev.c:5236
__do_softirq+0x31f/0xbe7 kernel/softirq.c:284
do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:902
</IRQ>
do_softirq.part.21+0x2c0/0x300 kernel/softirq.c:328
do_softirq kernel/softirq.c:176 [inline]
__local_bh_enable_ip+0x24c/0x290 kernel/softirq.c:181
local_bh_enable include/linux/bottom_half.h:31 [inline]
rcu_read_unlock_bh include/linux/rcupdate.h:971 [inline]
ip6_finish_output2+0xb85/0x2380 net/ipv6/ip6_output.c:124
ip6_finish_output+0x2f9/0x950 net/ipv6/ip6_output.c:149
NF_HOOK_COND include/linux/netfilter.h:246 [inline]
ip6_output+0x1cb/0x8c0 net/ipv6/ip6_output.c:163
ip6_xmit+0xc36/0x1e80 include/net/dst.h:486
inet6_csk_xmit+0x320/0x5d0 net/ipv6/inet6_connection_sock.c:139
dccp_transmit_skb+0xac5/0x10e0 net/dccp/output.c:141
dccp_send_ack+0x1bf/0x350 net/dccp/output.c:594
dccp_rcv_request_sent_state_process net/dccp/input.c:501 [inline]
dccp_rcv_state_process+0x102d/0x1650 net/dccp/input.c:671
dccp_v6_do_rcv+0x20d/0x350 net/dccp/ipv6.c:632
sk_backlog_rcv include/net/sock.h:896 [inline]
__release_sock+0x126/0x3a0 net/core/sock.c:2052
release_sock+0xa5/0x2b0 net/core/sock.c:2539
inet_wait_for_connect net/ipv4/af_inet.c:557 [inline]
__inet_stream_connect+0x712/0xf80 net/ipv4/af_inet.c:643
inet_stream_connect+0x58/0xa0 net/ipv4/af_inet.c:682
SYSC_connect+0x251/0x580 net/socket.c:1577
SyS_connect+0x24/0x30 net/socket.c:1558
entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x4458d9
RSP: 002b:00007fbd320fbb58 EFLAGS: 00000282 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 0000000000000020 RCX: 00000000004458d9
RDX: 0000000000000020 RSI: 0000000020e5afe0 RDI: 0000000000000020
RBP: 00000000006de450 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000282 R12: 00000000007080a8
R13: 0000000000000001 R14: 00000000007080b0 R15: 00007fbd320fc700


It seems that dccp_create_openreq_child needs to unlock the sock if
dccp_feat_activate_values fails.

[Arnaldo Carvalho de Melo]

Em Wed, Mar 01, 2017 at 10:38:54AM +0100, Dmitry Vyukov escreveu:
> Hello,
>
> I've got the following report while running syzkaller fuzzer on
> 86292b33d4b79ee03e2f43ea0381ef85f077c760:
>
>

> It seems that dccp_create_openreq_child needs to unlock the sock if
> dccp_feat_activate_values fails.

Yeah, can you please use the patch below, that mimics the error paths in
sk_clone_new(), from where I think even the comment about it being a raw
copy came, but the bh_unlock_sock() didn't?

- Arnaldo

diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index 53eddf99e4f6..d20d948a98ed 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -122,6 +122,7 @@ struct sock *dccp_create_openreq_child(const struct sock *sk,
/* It is still raw copy of parent, so invalidate
* destructor and make plain sk_free() */
newsk->sk_destruct = NULL;
+ bh_unlock_sock(newsk);
sk_free(newsk);
return NULL;
}

[Arnaldo Carvalho de Melo]

Em Wed, Mar 01, 2017 at 12:35:10PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Wed, Mar 01, 2017 at 10:38:54AM +0100, Dmitry Vyukov escreveu:
> > Hello,
> >
> > I've got the following report while running syzkaller fuzzer on
> > 86292b33d4b79ee03e2f43ea0381ef85f077c760:
> >
> >
> > It seems that dccp_create_openreq_child needs to unlock the sock if
> > dccp_feat_activate_values fails.
>
> Yeah, can you please use the patch below, that mimics the error paths in
> sk_clone_new(), from where I think even the comment about it being a raw

Argh, s/sk_clone_new()/sk_clone_lock()/g

- Arnaldo

[Dmitry Vyukov]

Applied the patch on bots. Will report if it happens again.

[Andrey Konovalov]

On Wed, Mar 1, 2017 at 4:40 PM, Arnaldo Carvalho de Melo
<ac...@kernel.org> wrote:
> Em Wed, Mar 01, 2017 at 12:35:10PM -0300, Arnaldo Carvalho de Melo escreveu:
>> Em Wed, Mar 01, 2017 at 10:38:54AM +0100, Dmitry Vyukov escreveu:
>> > Hello,
>> >
>> > I've got the following report while running syzkaller fuzzer on
>> > 86292b33d4b79ee03e2f43ea0381ef85f077c760:
>> >
>> >
>> > It seems that dccp_create_openreq_child needs to unlock the sock if
>> > dccp_feat_activate_values fails.
>>
>> Yeah, can you please use the patch below, that mimics the error paths in
>> sk_clone_new(), from where I think even the comment about it being a raw
>
> Argh, s/sk_clone_new()/sk_clone_lock()/g

Hi Arnaldo,

Could you send the patch?

We haven't seen these reports since we applied it.

Thanks!

>
> - Arnaldo
>
>> copy came, but the bh_unlock_sock() didn't?
>>
>> - Arnaldo
>>
>> diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
>> index 53eddf99e4f6..d20d948a98ed 100644
>> --- a/net/dccp/minisocks.c
>> +++ b/net/dccp/minisocks.c
>> @@ -122,6 +122,7 @@ struct sock *dccp_create_openreq_child(const struct sock *sk,
>> /* It is still raw copy of parent, so invalidate
>> * destructor and make plain sk_free() */
>> newsk->sk_destruct = NULL;
>> + bh_unlock_sock(newsk);
>> sk_free(newsk);
>> return NULL;
>> }
>

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[David Miller]

From: Andrey Konovalov <andre...@google.com>
Date: Thu, 4 May 2017 15:36:37 +0200

> On Wed, Mar 1, 2017 at 4:40 PM, Arnaldo Carvalho de Melo
> <ac...@kernel.org> wrote:
>> Em Wed, Mar 01, 2017 at 12:35:10PM -0300, Arnaldo Carvalho de Melo escreveu:
>>> Em Wed, Mar 01, 2017 at 10:38:54AM +0100, Dmitry Vyukov escreveu:
>>> > Hello,
>>> >
>>> > I've got the following report while running syzkaller fuzzer on
>>> > 86292b33d4b79ee03e2f43ea0381ef85f077c760:
>>> >
>>> >
>>> > It seems that dccp_create_openreq_child needs to unlock the sock if
>>> > dccp_feat_activate_values fails.
>>>
>>> Yeah, can you please use the patch below, that mimics the error paths in
>>> sk_clone_new(), from where I think even the comment about it being a raw
>>
>> Argh, s/sk_clone_new()/sk_clone_lock()/g
>
> Hi Arnaldo,
>
> Could you send the patch?
>
> We haven't seen these reports since we applied it.

It isn't necessary in the current tree.

Arnaldo created a helper sk_free_unlock_clone() which handles this situation
properly, and calls it from dccp_create_openreq_child().

[Andrey Konovalov]

OK, great, thanks!