Re: [PATCH v2] ipc/mqueue: fix potential sleeping issue in mqueue_flush_file

[shaozhengchao <shaozhengchao@huawei.com>]

+ping

Does anyone have ideas with this patch?

On 2023/12/20 10:12, 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 mutex
> lock instead of spin lock in mqueue_flush_file.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> ---
> v2: CCed some networking maintainer & netdev list
> ---
>   ipc/mqueue.c | 48 ++++++++++++++++++++++++------------------------
>   1 file changed, 24 insertions(+), 24 deletions(-)
> 
> diff --git a/ipc/mqueue.c b/ipc/mqueue.c
> index 5eea4dc0509e..f6f92e3f82e4 100644
> --- a/ipc/mqueue.c
> +++ b/ipc/mqueue.c
> @@ -118,9 +118,9 @@ struct posix_msg_tree_node {
>    * Solution: use _release and _acquire barriers.
>    *
>    * 3) There is intentionally no barrier when setting current->state
> - *    to TASK_INTERRUPTIBLE: spin_unlock(&info->lock) provides the
> + *    to TASK_INTERRUPTIBLE: mutex_unlock(&info->lock) provides the
>    *    release memory barrier, and the wakeup is triggered when holding
> - *    info->lock, i.e. spin_lock(&info->lock) provided a pairing
> + *    info->lock, i.e. mutex_lock(&info->lock) provided a pairing
>    *    acquire memory barrier.
>    */
>   
> @@ -132,7 +132,7 @@ struct ext_wait_queue {		/* queue of sleeping tasks */
>   };
>   
>   struct mqueue_inode_info {
> -	spinlock_t lock;
> +	struct mutex lock;
>   	struct inode vfs_inode;
>   	wait_queue_head_t wait_q;
>   
> @@ -312,7 +312,7 @@ static struct inode *mqueue_get_inode(struct super_block *sb,
>   		inode->i_size = FILENT_SIZE;
>   		/* mqueue specific info */
>   		info = MQUEUE_I(inode);
> -		spin_lock_init(&info->lock);
> +		mutex_init(&info->lock);
>   		init_waitqueue_head(&info->wait_q);
>   		INIT_LIST_HEAD(&info->e_wait_q[0].list);
>   		INIT_LIST_HEAD(&info->e_wait_q[1].list);
> @@ -523,11 +523,11 @@ static void mqueue_evict_inode(struct inode *inode)
>   
>   	ipc_ns = get_ns_from_inode(inode);
>   	info = MQUEUE_I(inode);
> -	spin_lock(&info->lock);
> +	mutex_lock(&info->lock);
>   	while ((msg = msg_get(info)) != NULL)
>   		list_add_tail(&msg->m_list, &tmp_msg);
>   	kfree(info->node_cache);
> -	spin_unlock(&info->lock);
> +	mutex_unlock(&info->lock);
>   
>   	list_for_each_entry_safe(msg, nmsg, &tmp_msg, m_list) {
>   		list_del(&msg->m_list);
> @@ -640,7 +640,7 @@ static ssize_t mqueue_read_file(struct file *filp, char __user *u_data,
>   	char buffer[FILENT_SIZE];
>   	ssize_t ret;
>   
> -	spin_lock(&info->lock);
> +	mutex_lock(&info->lock);
>   	snprintf(buffer, sizeof(buffer),
>   			"QSIZE:%-10lu NOTIFY:%-5d SIGNO:%-5d NOTIFY_PID:%-6d\n",
>   			info->qsize,
> @@ -649,7 +649,7 @@ static ssize_t mqueue_read_file(struct file *filp, char __user *u_data,
>   			 info->notify.sigev_notify == SIGEV_SIGNAL) ?
>   				info->notify.sigev_signo : 0,
>   			pid_vnr(info->notify_owner));
> -	spin_unlock(&info->lock);
> +	mutex_unlock(&info->lock);
>   	buffer[sizeof(buffer)-1] = '\0';
>   
>   	ret = simple_read_from_buffer(u_data, count, off, buffer,
> @@ -665,11 +665,11 @@ static int mqueue_flush_file(struct file *filp, fl_owner_t id)
>   {
>   	struct mqueue_inode_info *info = MQUEUE_I(file_inode(filp));
>   
> -	spin_lock(&info->lock);
> +	mutex_lock(&info->lock);
>   	if (task_tgid(current) == info->notify_owner)
>   		remove_notification(info);
>   
> -	spin_unlock(&info->lock);
> +	mutex_unlock(&info->lock);
>   	return 0;
>   }
>   
> @@ -680,13 +680,13 @@ static __poll_t mqueue_poll_file(struct file *filp, struct poll_table_struct *po
>   
>   	poll_wait(filp, &info->wait_q, poll_tab);
>   
> -	spin_lock(&info->lock);
> +	mutex_lock(&info->lock);
>   	if (info->attr.mq_curmsgs)
>   		retval = EPOLLIN | EPOLLRDNORM;
>   
>   	if (info->attr.mq_curmsgs < info->attr.mq_maxmsg)
>   		retval |= EPOLLOUT | EPOLLWRNORM;
> -	spin_unlock(&info->lock);
> +	mutex_unlock(&info->lock);
>   
>   	return retval;
>   }
> @@ -724,7 +724,7 @@ static int wq_sleep(struct mqueue_inode_info *info, int sr,
>   		/* memory barrier not required, we hold info->lock */
>   		__set_current_state(TASK_INTERRUPTIBLE);
>   
> -		spin_unlock(&info->lock);
> +		mutex_unlock(&info->lock);
>   		time = schedule_hrtimeout_range_clock(timeout, 0,
>   			HRTIMER_MODE_ABS, CLOCK_REALTIME);
>   
> @@ -734,7 +734,7 @@ static int wq_sleep(struct mqueue_inode_info *info, int sr,
>   			retval = 0;
>   			goto out;
>   		}
> -		spin_lock(&info->lock);
> +		mutex_lock(&info->lock);
>   
>   		/* we hold info->lock, so no memory barrier required */
>   		if (READ_ONCE(ewp->state) == STATE_READY) {
> @@ -752,7 +752,7 @@ static int wq_sleep(struct mqueue_inode_info *info, int sr,
>   	}
>   	list_del(&ewp->list);
>   out_unlock:
> -	spin_unlock(&info->lock);
> +	mutex_unlock(&info->lock);
>   out:
>   	return retval;
>   }
> @@ -1125,7 +1125,7 @@ static int do_mq_timedsend(mqd_t mqdes, const char __user *u_msg_ptr,
>   	if (!info->node_cache)
>   		new_leaf = kmalloc(sizeof(*new_leaf), GFP_KERNEL);
>   
> -	spin_lock(&info->lock);
> +	mutex_lock(&info->lock);
>   
>   	if (!info->node_cache && new_leaf) {
>   		/* Save our speculative allocation into the cache */
> @@ -1166,7 +1166,7 @@ static int do_mq_timedsend(mqd_t mqdes, const char __user *u_msg_ptr,
>   		simple_inode_init_ts(inode);
>   	}
>   out_unlock:
> -	spin_unlock(&info->lock);
> +	mutex_unlock(&info->lock);
>   	wake_up_q(&wake_q);
>   out_free:
>   	if (ret)
> @@ -1230,7 +1230,7 @@ static int do_mq_timedreceive(mqd_t mqdes, char __user *u_msg_ptr,
>   	if (!info->node_cache)
>   		new_leaf = kmalloc(sizeof(*new_leaf), GFP_KERNEL);
>   
> -	spin_lock(&info->lock);
> +	mutex_lock(&info->lock);
>   
>   	if (!info->node_cache && new_leaf) {
>   		/* Save our speculative allocation into the cache */
> @@ -1242,7 +1242,7 @@ static int do_mq_timedreceive(mqd_t mqdes, char __user *u_msg_ptr,
>   
>   	if (info->attr.mq_curmsgs == 0) {
>   		if (f.file->f_flags & O_NONBLOCK) {
> -			spin_unlock(&info->lock);
> +			mutex_unlock(&info->lock);
>   			ret = -EAGAIN;
>   		} else {
>   			wait.task = current;
> @@ -1261,7 +1261,7 @@ static int do_mq_timedreceive(mqd_t mqdes, char __user *u_msg_ptr,
>   
>   		/* There is now free space in queue. */
>   		pipelined_receive(&wake_q, info);
> -		spin_unlock(&info->lock);
> +		mutex_unlock(&info->lock);
>   		wake_up_q(&wake_q);
>   		ret = 0;
>   	}
> @@ -1391,7 +1391,7 @@ static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)
>   	info = MQUEUE_I(inode);
>   
>   	ret = 0;
> -	spin_lock(&info->lock);
> +	mutex_lock(&info->lock);
>   	if (notification == NULL) {
>   		if (info->notify_owner == task_tgid(current)) {
>   			remove_notification(info);
> @@ -1424,7 +1424,7 @@ static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)
>   		info->notify_user_ns = get_user_ns(current_user_ns());
>   		inode_set_atime_to_ts(inode, inode_set_ctime_current(inode));
>   	}
> -	spin_unlock(&info->lock);
> +	mutex_unlock(&info->lock);
>   out_fput:
>   	fdput(f);
>   out:
> @@ -1470,7 +1470,7 @@ static int do_mq_getsetattr(int mqdes, struct mq_attr *new, struct mq_attr *old)
>   	inode = file_inode(f.file);
>   	info = MQUEUE_I(inode);
>   
> -	spin_lock(&info->lock);
> +	mutex_lock(&info->lock);
>   
>   	if (old) {
>   		*old = info->attr;
> @@ -1488,7 +1488,7 @@ static int do_mq_getsetattr(int mqdes, struct mq_attr *new, struct mq_attr *old)
>   		inode_set_atime_to_ts(inode, inode_set_ctime_current(inode));
>   	}
>   
> -	spin_unlock(&info->lock);
> +	mutex_unlock(&info->lock);
>   	fdput(f);
>   	return 0;
>   }