On Sat, Dec 3, 2016 at 9:41 AM, Cong Wang <xiyou.wangc...@gmail.com> wrote:
> On Sat, Dec 3, 2016 at 4:56 AM, Andrey Konovalov <andreyk...@google.com>
> wrote:
>> Hi!
>>
>> I'm seeing lots of the following error reports while running the
>> syzkaller fuzzer.
>>
>> Reports appeared when I updated to 3c49de52 (Dec 2) from 2caceb32 (Dec 1).
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in worker_thread+0x17d8/0x18a0
>> Read of size 8 at addr ffff880067f3ecd8 by task kworker/3:1/774
>>
>> page:ffffea00019fce00 count:1 mapcount:0 mapping: (null)
>> index:0xffff880067f39c10 compound_mapcount: 0
>> flags: 0x500000000004080(slab|head)
>> page dumped because: kasan: bad access detected
>>
>> CPU: 3 PID: 774 Comm: kworker/3:1 Not tainted 4.9.0-rc7+ #66
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>> ffff88006c267838 ffffffff81f882da ffffffff6c25e338 1ffff1000d84ce9a
>> ffffed000d84ce92 ffff88006c25e340 0000000041b58ab3 ffffffff8541e198
>> ffffffff81f88048 0000000100000000 0000000041b58ab3 ffffffff853d3ee8
>> Call Trace:
>> [< inline >] __dump_stack lib/dump_stack.c:15
>> [<ffffffff81f882da>] dump_stack+0x292/0x398 lib/dump_stack.c:51
>> [< inline >] describe_address mm/kasan/report.c:262
>> [<ffffffff817e50d1>] kasan_report_error+0x121/0x560 mm/kasan/report.c:368
>> [< inline >] kasan_report mm/kasan/report.c:390
>> [<ffffffff817e560e>] __asan_report_load8_noabort+0x3e/0x40
>> mm/kasan/report.c:411
>> [<ffffffff81329b88>] worker_thread+0x17d8/0x18a0 kernel/workqueue.c:2228
>> [<ffffffff8133ebf3>] kthread+0x323/0x3e0 kernel/kthread.c:209
>> [<ffffffff84a2a22a>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
>
> Heck... this is the pending work vs. sk_destruct() race. :-/
> We can't wait for the work in RCU callback, let me think about it...
Please try the attached patch, I only did compile test, I can't access
my desktop now, so can't do further tests.
Thanks!
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 602e5eb..6f33013 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -322,11 +322,13 @@ static void netlink_skb_set_owner_r(struct sk_buff *skb,
struct sock *sk)
sk_mem_charge(sk, skb->truesize);
}
-static void __netlink_sock_destruct(struct sock *sk)
+static void netlink_sock_destruct(struct sock *sk)
{
struct netlink_sock *nlk = nlk_sk(sk);
if (nlk->cb_running) {
+ if (nlk->cb.done)
+ nlk->cb.done(&nlk->cb);
module_put(nlk->cb.module);
kfree_skb(nlk->cb.skb);
}
@@ -343,28 +345,6 @@ static void __netlink_sock_destruct(struct sock *sk)
WARN_ON(nlk_sk(sk)->groups);
}
-static void netlink_sock_destruct_work(struct work_struct *work)
-{
- struct netlink_sock *nlk = container_of(work, struct netlink_sock,
- work);
-
- nlk->cb.done(&nlk->cb);
- __netlink_sock_destruct(&nlk->sk);
-}
-
-static void netlink_sock_destruct(struct sock *sk)
-{
- struct netlink_sock *nlk = nlk_sk(sk);
-
- if (nlk->cb_running && nlk->cb.done) {
- INIT_WORK(&nlk->work, netlink_sock_destruct_work);
- schedule_work(&nlk->work);
- return;
- }
-
- __netlink_sock_destruct(sk);
-}
-
/* This lock without WQ_FLAG_EXCLUSIVE is good on UP and it is _very_ bad on
* SMP. Look, when several writers sleep and reader wakes them up, all but one
* immediately hit write lock and grab all the cpus. Exclusive sleep solves
@@ -664,11 +644,19 @@ static int netlink_create(struct net *net, struct socket
*sock, int protocol,
goto out;
}
+static void netlink_sock_put_work(struct work_struct *work)
+{
+ struct netlink_sock *nlk = container_of(work, struct netlink_sock,
+ work);
+ sock_put(&nlk->sk);
+}
+
static void deferred_put_nlk_sk(struct rcu_head *head)
{
struct netlink_sock *nlk = container_of(head, struct netlink_sock, rcu);
- sock_put(&nlk->sk);
+ INIT_WORK(&nlk->work, netlink_sock_put_work);
+ schedule_work(&nlk->work);
}
static int netlink_release(struct socket *sock)
