[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <Za4t110BCZAnlf1o@calendula>
Date: Mon, 22 Jan 2024 09:56:55 +0100
From: Pablo Neira Ayuso <pablo@...filter.org>
To: Zhengchao Shao <shaozhengchao@...wei.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
kuba@...nel.org, pabeni@...hat.com, horms@...nel.org,
anjali.k.kulkarni@...cle.com, kuniyu@...zon.com, fw@...len.de,
weiyongjun1@...wei.com, yuehaibing@...wei.com
Subject: Re: [PATCH net,v4] netlink: fix potential sleeping issue in
mqueue_flush_file
On Mon, Jan 22, 2024 at 09:18:07AM +0800, Zhengchao Shao wrote:
> I analyze the potential sleeping issue of the following processes:
> Thread A Thread B
> ... netlink_create //ref = 1
> do_mq_notify ...
> sock = netlink_getsockbyfilp ... //ref = 2
> info->notify_sock = sock; ...
> ... netlink_sendmsg
> ... skb = netlink_alloc_large_skb //skb->head is vmalloced
> ... netlink_unicast
> ... sk = netlink_getsockbyportid //ref = 3
> ... netlink_sendskb
> ... __netlink_sendskb
> ... skb_queue_tail //put skb to sk_receive_queue
> ... sock_put //ref = 2
> ... ...
> ... netlink_release
> ... deferred_put_nlk_sk //ref = 1
> mqueue_flush_file
> spin_lock
> remove_notification
> netlink_sendskb
> sock_put //ref = 0
> sk_free
> ...
> __sk_destruct
> netlink_sock_destruct
> skb_queue_purge //get skb from sk_receive_queue
> ...
> __skb_queue_purge_reason
> kfree_skb_reason
> __kfree_skb
> ...
> skb_release_all
> skb_release_head_state
> netlink_skb_destructor
> vfree(skb->head) //sleeping while holding spinlock
>
> In netlink_sendmsg, if the memory pointed to by skb->head is allocated by
> vmalloc, and is put to sk_receive_queue queue, also the skb is not freed.
> When the mqueue executes flush, the sleeping bug will occur. Use
> vfree_atomic instead of vfree in netlink_skb_destructor to solve the issue.
mqueue notification is of NOTIFY_COOKIE_LEN size:
static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)
{
[...]
if (notification->sigev_notify == SIGEV_THREAD) {
long timeo;
/* create the notify skb */
nc = alloc_skb(NOTIFY_COOKIE_LEN, GFP_KERNEL);
if (!nc)
return -ENOMEM;
Do you have a reproducer?
Powered by blists - more mailing lists