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Date: Tue, 19 Dec 2023 15:15:19 +0800
From: shaozhengchao <shaozhengchao@...wei.com>
To: Jan Kara <jack@...e.cz>
CC: <gregkh@...uxfoundation.org>, <brauner@...nel.org>, <dchinner@...hat.com>,
<jlayton@...nel.org>, <riel@...riel.com>, <weiyongjun1@...wei.com>,
<yuehaibing@...wei.com>, <netdev@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, Jakub Kicinski <kuba@...nel.org>
Subject: Re: [RESEND PATCH] ipc/mqueue: fix potential sleeping issue in
mqueue_flush_file
On 2023/12/18 21:08, Jan Kara wrote:
> [CCed some networking people & netdev list since this is closely related to
> networking]
>
> On Mon 18-12-23 11:06:24, Zhengchao Shao wrote:
>> I analyze the potential sleeping issue of the following processes:
>> Thread A Thread B
>> ... netlink_create //create sock
>> do_mq_notify ...
>> sock = netlink_getsockbyfilp ... //hold sock
>> info->notify_sock = sock; ...
>> ... netlink_sendmsg
>> ... skb = netlink_alloc_large_skb //skb->head is vmalloced
>> ... netlink_unicast
>> ... sk = netlink_getsockbyportid
>> ... netlink_sendskb
>> ... __netlink_sendskb
>> ... skb_queue_tail //put skb to sk_receive_queue
>> mqueue_flush_file
>> spin_lock
>> remove_notification
>> netlink_sendskb
>> sock_put //put sock
>> 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@...wei.com>
>
Hi Jan Kara:
> I guess you are not getting answers because ipc/mqueue.c has no clear
> maintainer and at least I know nothing about mqueue and only very little
> about netlink which is also involved here. Do I get it right this was
Thank you for your advice. I'll cc the maintainer in the network
field in v2.
> spotted by some checker, not really causing problems in the wild?
This is an issue with syzkaller running on the 5.10 kernel, and it
happened only once. And I analyze the mainline tree code, and there's
the same issue.
>
> Another question (and this is why I've involved the networking people): Is
> it really possible that we end up calling sk_free() from under
> mqueue_flush_file() - at the time this is called we are closing the file
> but it is not closed yet which means the socket inode is pretty much alive
> which I'd *think* means there is still somebody holding socket reference
> and thus sock_put() will not drop the last socket reference... Am I missing
> something?
Sorry, I forgot to add the netlink release process. The following figure
shows a better explanation of how the issue occurred.
Thread A Thread B
... netlink_create //ref = 1
do_mq_notify ...
sock = netlink_getsockbyfilp ... //hold sock, ref = 2
info->notify_sock = sock; ...
... netlink_sendmsg
... skb = netlink_alloc_large_skb
//skb->head is vmalloced
... netlink_unicast
... sk = netlink_getsockbyportid
//hold sock, 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 //put sock, 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
Isn't that a little clearer?
Thank you.
Zhengchao Shao
>
> Honza
>
>> ---
>> 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;
>> }
>> --
>> 2.34.1
>>
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