Commit 839028bc authored by Ye Bin's avatar Ye Bin Committed by Yang Yingliang
Browse files

nbd: Fix use-after-free in pid_show 



mainline inclusion
from mainline-v5.16
commit 0c98057b
category: bugfix
bugzilla: 182939
CVE: NA

-----------------------------------------------

I got issue as follows:
[  263.886511] BUG: KASAN: use-after-free in pid_show+0x11f/0x13f
[  263.888359] Read of size 4 at addr ffff8880bf0648c0 by task cat/746
[  263.890479] CPU: 0 PID: 746 Comm: cat Not tainted 4.19.90-dirty #140
[  263.893162] Call Trace:
[  263.893509]  dump_stack+0x108/0x15f
[  263.893999]  print_address_description+0xa5/0x372
[  263.894641]  kasan_report.cold+0x236/0x2a8
[  263.895696]  __asan_report_load4_noabort+0x25/0x30
[  263.896365]  pid_show+0x11f/0x13f
[  263.897422]  dev_attr_show+0x48/0x90
[  263.898361]  sysfs_kf_seq_show+0x24d/0x4b0
[  263.899479]  kernfs_seq_show+0x14e/0x1b0
[  263.900029]  seq_read+0x43f/0x1150
[  263.900499]  kernfs_fop_read+0xc7/0x5a0
[  263.903764]  vfs_read+0x113/0x350
[  263.904231]  ksys_read+0x103/0x270
[  263.905230]  __x64_sys_read+0x77/0xc0
[  263.906284]  do_syscall_64+0x106/0x360
[  263.906797]  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reproduce this issue as follows:
1. nbd-server 8000 /tmp/disk
2. nbd-client localhost 8000 /dev/nbd1
3. cat /sys/block/nbd1/pid
Then trigger use-after-free in pid_show.

Reason is after do step '2', nbd-client progress is already exit. So
it's task_struct already freed.
To solve this issue, revert part of 6521d39a's modify and remove
useless 'recv_task' member of nbd_device.

Fixes: 6521d39a ("nbd: Remove variable 'pid'")
Signed-off-by: default avatarYe Bin <yebin10@huawei.com>
Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20211020073959.2679255-1-yebin10@huawei.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>

conflicts:
drivers/block/nbd.c

Signed-off-by: default avatarYe Bin <yebin10@huawei.com>
Reviewed-by: default avatarJason Yan <yanaijie@huawei.com>
Signed-off-by: default avatarYang Yingliang <yangyingliang@huawei.com>
parent ffceb572

drivers/block/nbd.c

+9 −9
Original line number Diff line number Diff line
@@ -112,11 +112,11 @@ struct nbd_device { 
	struct workqueue_struct *recv_workq;



	struct list_head list;

	struct task_struct *task_recv;

	struct task_struct *task_setup;



	struct completion *destroy_complete;

	unsigned long flags;

	pid_t pid; /* pid of nbd-client, if attached */

};



#define NBD_CMD_REQUEUED	1
@@ -211,7 +211,7 @@ static ssize_t pid_show(struct device *dev, 
	struct gendisk *disk = dev_to_disk(dev);

	struct nbd_device *nbd = (struct nbd_device *)disk->private_data;



	return sprintf(buf, "%d\n", task_pid_nr(nbd->task_recv));

	return sprintf(buf, "%d\n", nbd->pid);

}



static const struct device_attribute pid_attr = {
@@ -329,7 +329,7 @@ static void nbd_size_set(struct nbd_device *nbd, loff_t blocksize, 
	struct nbd_config *config = nbd->config;

	config->blksize = blocksize;

	config->bytesize = blocksize * nr_blocks;

	if (nbd->task_recv != NULL)

	if (nbd->pid)

		nbd_size_update(nbd, false);

}
@@ -1234,7 +1234,7 @@ static void nbd_config_put(struct nbd_device *nbd) 
		if (test_and_clear_bit(NBD_RT_HAS_PID_FILE,

				       &config->runtime_flags))

			device_remove_file(disk_to_dev(nbd->disk), &pid_attr);

		nbd->task_recv = NULL;

		nbd->pid = 0;

		nbd_clear_sock(nbd);

		if (config->num_connections) {

			int i;
@@ -1269,7 +1269,7 @@ static int nbd_start_device(struct nbd_device *nbd) 
	int num_connections = config->num_connections;

	int error = 0, i;



	if (nbd->task_recv)

	if (nbd->pid)

		return -EBUSY;

	if (!config->socks)

		return -EINVAL;
@@ -1288,7 +1288,7 @@ static int nbd_start_device(struct nbd_device *nbd) 
	}



	blk_mq_update_nr_hw_queues(&nbd->tag_set, config->num_connections);

	nbd->task_recv = current;

	nbd->pid = task_pid_nr(current);



	nbd_parse_flags(nbd);
@@ -1546,8 +1546,8 @@ static int nbd_dbg_tasks_show(struct seq_file *s, void *unused) 
{

	struct nbd_device *nbd = s->private;



	if (nbd->task_recv)

		seq_printf(s, "recv: %d\n", task_pid_nr(nbd->task_recv));

	if (nbd->pid)

		seq_printf(s, "recv: %d\n", nbd->pid);



	return 0;

}
@@ -2106,7 +2106,7 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info) 
	mutex_lock(&nbd->config_lock);

	config = nbd->config;

	if (!test_bit(NBD_RT_BOUND, &config->runtime_flags) ||

	    !nbd->task_recv) {

	    !nbd->pid) {

		dev_err(nbd_to_dev(nbd),

			"not configured, cannot reconfigure\n");

		ret = -EINVAL;