* [PATCH net] netlink: fix an use-after-free issue for nlk groups
@ 2017-09-06 3:47 Xin Long
2017-09-07 4:24 ` David Miller
2017-09-08 21:56 ` Cong Wang
0 siblings, 2 replies; 4+ messages in thread
From: Xin Long @ 2017-09-06 3:47 UTC (permalink / raw)
To: network dev; +Cc: davem, fw, chunwang, syzkaller
ChunYu found a netlink use-after-free issue by syzkaller:
[28448.842981] BUG: KASAN: use-after-free in __nla_put+0x37/0x40 at addr ffff8807185e2378
[28448.969918] Call Trace:
[...]
[28449.117207] __nla_put+0x37/0x40
[28449.132027] nla_put+0xf5/0x130
[28449.146261] sk_diag_fill.isra.4.constprop.5+0x5a0/0x750 [netlink_diag]
[28449.176608] __netlink_diag_dump+0x25a/0x700 [netlink_diag]
[28449.202215] netlink_diag_dump+0x176/0x240 [netlink_diag]
[28449.226834] netlink_dump+0x488/0xbb0
[28449.298014] __netlink_dump_start+0x4e8/0x760
[28449.317924] netlink_diag_handler_dump+0x261/0x340 [netlink_diag]
[28449.413414] sock_diag_rcv_msg+0x207/0x390
[28449.432409] netlink_rcv_skb+0x149/0x380
[28449.467647] sock_diag_rcv+0x2d/0x40
[28449.484362] netlink_unicast+0x562/0x7b0
[28449.564790] netlink_sendmsg+0xaa8/0xe60
[28449.661510] sock_sendmsg+0xcf/0x110
[28449.865631] __sys_sendmsg+0xf3/0x240
[28450.000964] SyS_sendmsg+0x32/0x50
[28450.016969] do_syscall_64+0x25c/0x6c0
[28450.154439] entry_SYSCALL64_slow_path+0x25/0x25
It was caused by no protection between nlk groups' free in netlink_release
and nlk groups' accessing in sk_diag_dump_groups. The similar issue also
exists in netlink_seq_show().
This patch is to defer nlk groups' free in deferred_put_nlk_sk.
Reported-by: ChunYu Wang <chunwang@redhat.com>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
net/netlink/af_netlink.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 5acee49..94a61e6 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -691,6 +691,9 @@ static void deferred_put_nlk_sk(struct rcu_head *head)
struct netlink_sock *nlk = container_of(head, struct netlink_sock, rcu);
struct sock *sk = &nlk->sk;
+ kfree(nlk->groups);
+ nlk->groups = NULL;
+
if (!refcount_dec_and_test(&sk->sk_refcnt))
return;
@@ -769,9 +772,6 @@ static int netlink_release(struct socket *sock)
netlink_table_ungrab();
}
- kfree(nlk->groups);
- nlk->groups = NULL;
-
local_bh_disable();
sock_prot_inuse_add(sock_net(sk), &netlink_proto, -1);
local_bh_enable();
--
2.1.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH net] netlink: fix an use-after-free issue for nlk groups
2017-09-06 3:47 [PATCH net] netlink: fix an use-after-free issue for nlk groups Xin Long
@ 2017-09-07 4:24 ` David Miller
2017-09-08 21:56 ` Cong Wang
1 sibling, 0 replies; 4+ messages in thread
From: David Miller @ 2017-09-07 4:24 UTC (permalink / raw)
To: lucien.xin; +Cc: netdev, fw, chunwang, syzkaller
From: Xin Long <lucien.xin@gmail.com>
Date: Wed, 6 Sep 2017 11:47:12 +0800
> ChunYu found a netlink use-after-free issue by syzkaller:
>
> [28448.842981] BUG: KASAN: use-after-free in __nla_put+0x37/0x40 at addr ffff8807185e2378
> [28448.969918] Call Trace:
> [...]
> [28449.117207] __nla_put+0x37/0x40
> [28449.132027] nla_put+0xf5/0x130
> [28449.146261] sk_diag_fill.isra.4.constprop.5+0x5a0/0x750 [netlink_diag]
> [28449.176608] __netlink_diag_dump+0x25a/0x700 [netlink_diag]
> [28449.202215] netlink_diag_dump+0x176/0x240 [netlink_diag]
> [28449.226834] netlink_dump+0x488/0xbb0
> [28449.298014] __netlink_dump_start+0x4e8/0x760
> [28449.317924] netlink_diag_handler_dump+0x261/0x340 [netlink_diag]
> [28449.413414] sock_diag_rcv_msg+0x207/0x390
> [28449.432409] netlink_rcv_skb+0x149/0x380
> [28449.467647] sock_diag_rcv+0x2d/0x40
> [28449.484362] netlink_unicast+0x562/0x7b0
> [28449.564790] netlink_sendmsg+0xaa8/0xe60
> [28449.661510] sock_sendmsg+0xcf/0x110
> [28449.865631] __sys_sendmsg+0xf3/0x240
> [28450.000964] SyS_sendmsg+0x32/0x50
> [28450.016969] do_syscall_64+0x25c/0x6c0
> [28450.154439] entry_SYSCALL64_slow_path+0x25/0x25
>
> It was caused by no protection between nlk groups' free in netlink_release
> and nlk groups' accessing in sk_diag_dump_groups. The similar issue also
> exists in netlink_seq_show().
>
> This patch is to defer nlk groups' free in deferred_put_nlk_sk.
>
> Reported-by: ChunYu Wang <chunwang@redhat.com>
> Acked-by: Florian Westphal <fw@strlen.de>
> Signed-off-by: Xin Long <lucien.xin@gmail.com>
Applied.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net] netlink: fix an use-after-free issue for nlk groups
2017-09-06 3:47 [PATCH net] netlink: fix an use-after-free issue for nlk groups Xin Long
2017-09-07 4:24 ` David Miller
@ 2017-09-08 21:56 ` Cong Wang
2017-09-10 12:02 ` Xin Long
1 sibling, 1 reply; 4+ messages in thread
From: Cong Wang @ 2017-09-08 21:56 UTC (permalink / raw)
To: Xin Long; +Cc: network dev, David Miller, Florian Westphal, chunwang, syzkaller
On Tue, Sep 5, 2017 at 8:47 PM, Xin Long <lucien.xin@gmail.com> wrote:
> ChunYu found a netlink use-after-free issue by syzkaller:
>
> [28448.842981] BUG: KASAN: use-after-free in __nla_put+0x37/0x40 at addr ffff8807185e2378
> [28448.969918] Call Trace:
> [...]
> [28449.117207] __nla_put+0x37/0x40
> [28449.132027] nla_put+0xf5/0x130
> [28449.146261] sk_diag_fill.isra.4.constprop.5+0x5a0/0x750 [netlink_diag]
> [28449.176608] __netlink_diag_dump+0x25a/0x700 [netlink_diag]
> [28449.202215] netlink_diag_dump+0x176/0x240 [netlink_diag]
> [28449.226834] netlink_dump+0x488/0xbb0
> [28449.298014] __netlink_dump_start+0x4e8/0x760
> [28449.317924] netlink_diag_handler_dump+0x261/0x340 [netlink_diag]
> [28449.413414] sock_diag_rcv_msg+0x207/0x390
> [28449.432409] netlink_rcv_skb+0x149/0x380
> [28449.467647] sock_diag_rcv+0x2d/0x40
> [28449.484362] netlink_unicast+0x562/0x7b0
> [28449.564790] netlink_sendmsg+0xaa8/0xe60
> [28449.661510] sock_sendmsg+0xcf/0x110
> [28449.865631] __sys_sendmsg+0xf3/0x240
> [28450.000964] SyS_sendmsg+0x32/0x50
> [28450.016969] do_syscall_64+0x25c/0x6c0
> [28450.154439] entry_SYSCALL64_slow_path+0x25/0x25
>
> It was caused by no protection between nlk groups' free in netlink_release
> and nlk groups' accessing in sk_diag_dump_groups. The similar issue also
> exists in netlink_seq_show().
>
> This patch is to defer nlk groups' free in deferred_put_nlk_sk.
This looks odd too, at least not complete.
The netlink sock itself is protected by RCU to speed up
the lookup path, but not necessarily nlk->groups, at least
I don't see rcu_dereference() in sk_diag_dump_groups().
And netlink_realloc_groups() needs fix too, right? Otherwise
krealloc() could reallocate a brand new memory and
existing readers will crash too?
I am afraid you need more work to make nlk->groups
RCU friendly. RCU is not just about call_rcu(), both
readers and writers need to use proper RCU API.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net] netlink: fix an use-after-free issue for nlk groups
2017-09-08 21:56 ` Cong Wang
@ 2017-09-10 12:02 ` Xin Long
0 siblings, 0 replies; 4+ messages in thread
From: Xin Long @ 2017-09-10 12:02 UTC (permalink / raw)
To: Cong Wang
Cc: network dev, David Miller, Florian Westphal, chunwang, syzkaller
On Sat, Sep 9, 2017 at 9:56 AM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
> On Tue, Sep 5, 2017 at 8:47 PM, Xin Long <lucien.xin@gmail.com> wrote:
>> ChunYu found a netlink use-after-free issue by syzkaller:
>>
>> [28448.842981] BUG: KASAN: use-after-free in __nla_put+0x37/0x40 at addr ffff8807185e2378
>> [28448.969918] Call Trace:
>> [...]
>> [28449.117207] __nla_put+0x37/0x40
>> [28449.132027] nla_put+0xf5/0x130
>> [28449.146261] sk_diag_fill.isra.4.constprop.5+0x5a0/0x750 [netlink_diag]
>> [28449.176608] __netlink_diag_dump+0x25a/0x700 [netlink_diag]
>> [28449.202215] netlink_diag_dump+0x176/0x240 [netlink_diag]
>> [28449.226834] netlink_dump+0x488/0xbb0
>> [28449.298014] __netlink_dump_start+0x4e8/0x760
>> [28449.317924] netlink_diag_handler_dump+0x261/0x340 [netlink_diag]
>> [28449.413414] sock_diag_rcv_msg+0x207/0x390
>> [28449.432409] netlink_rcv_skb+0x149/0x380
>> [28449.467647] sock_diag_rcv+0x2d/0x40
>> [28449.484362] netlink_unicast+0x562/0x7b0
>> [28449.564790] netlink_sendmsg+0xaa8/0xe60
>> [28449.661510] sock_sendmsg+0xcf/0x110
>> [28449.865631] __sys_sendmsg+0xf3/0x240
>> [28450.000964] SyS_sendmsg+0x32/0x50
>> [28450.016969] do_syscall_64+0x25c/0x6c0
>> [28450.154439] entry_SYSCALL64_slow_path+0x25/0x25
>>
>> It was caused by no protection between nlk groups' free in netlink_release
>> and nlk groups' accessing in sk_diag_dump_groups. The similar issue also
>> exists in netlink_seq_show().
>>
>> This patch is to defer nlk groups' free in deferred_put_nlk_sk.
>
> This looks odd too, at least not complete.
>
> The netlink sock itself is protected by RCU to speed up
> the lookup path, but not necessarily nlk->groups, at least
> I don't see rcu_dereference() in sk_diag_dump_groups().
> And netlink_realloc_groups() needs fix too, right? Otherwise
> krealloc() could reallocate a brand new memory and
> existing readers will crash too?
We knew it's not good, but this one is not so bad as the one in
netlink_release, as krealloc will not alloc new memory when
the new size < old size, so it may not cause crash.
I was planning to fix it as a long term. As you also said, here needs
more work for nlk->groups, including proper RCU api for readers.
I will check more.
Thanks.
>
> I am afraid you need more work to make nlk->groups
> RCU friendly. RCU is not just about call_rcu(), both
> readers and writers need to use proper RCU API.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2017-09-06 3:47 [PATCH net] netlink: fix an use-after-free issue for nlk groups Xin Long
2017-09-07 4:24 ` David Miller
2017-09-08 21:56 ` Cong Wang
2017-09-10 12:02 ` Xin Long
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