nbd: fix race between nbd_alloc_config() and module removal
[ Upstream commit c55b2b983b
]
When nbd module is being removing, nbd_alloc_config() may be
called concurrently by nbd_genl_connect(), although try_module_get()
will return false, but nbd_alloc_config() doesn't handle it.
The race may lead to the leak of nbd_config and its related
resources (e.g, recv_workq) and oops in nbd_read_stat() due
to the unload of nbd module as shown below:
BUG: kernel NULL pointer dereference, address: 0000000000000040
Oops: 0000 [#1] SMP PTI
CPU: 5 PID: 13840 Comm: kworker/u17:33 Not tainted 5.14.0+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
Workqueue: knbd16-recv recv_work [nbd]
RIP: 0010:nbd_read_stat.cold+0x130/0x1a4 [nbd]
Call Trace:
recv_work+0x3b/0xb0 [nbd]
process_one_work+0x1ed/0x390
worker_thread+0x4a/0x3d0
kthread+0x12a/0x150
ret_from_fork+0x22/0x30
Fixing it by checking the return value of try_module_get()
in nbd_alloc_config(). As nbd_alloc_config() may return ERR_PTR(-ENODEV),
assign nbd->config only when nbd_alloc_config() succeeds to ensure
the value of nbd->config is binary (valid or NULL).
Also adding a debug message to check the reference counter
of nbd_config during module removal.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20220521073749.3146892-3-yukuai3@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Родитель
cbeafa7a79
Коммит
71c142f910
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@ -1467,15 +1467,20 @@ static struct nbd_config *nbd_alloc_config(void)
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{
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struct nbd_config *config;
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if (!try_module_get(THIS_MODULE))
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return ERR_PTR(-ENODEV);
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config = kzalloc(sizeof(struct nbd_config), GFP_NOFS);
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if (!config)
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return NULL;
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if (!config) {
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module_put(THIS_MODULE);
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return ERR_PTR(-ENOMEM);
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}
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atomic_set(&config->recv_threads, 0);
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init_waitqueue_head(&config->recv_wq);
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init_waitqueue_head(&config->conn_wait);
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config->blksize_bits = NBD_DEF_BLKSIZE_BITS;
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atomic_set(&config->live_connections, 0);
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try_module_get(THIS_MODULE);
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return config;
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}
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@ -1502,12 +1507,13 @@ static int nbd_open(struct block_device *bdev, fmode_t mode)
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mutex_unlock(&nbd->config_lock);
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goto out;
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}
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config = nbd->config = nbd_alloc_config();
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if (!config) {
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ret = -ENOMEM;
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config = nbd_alloc_config();
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if (IS_ERR(config)) {
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ret = PTR_ERR(config);
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mutex_unlock(&nbd->config_lock);
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goto out;
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}
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nbd->config = config;
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refcount_set(&nbd->config_refs, 1);
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refcount_inc(&nbd->refs);
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mutex_unlock(&nbd->config_lock);
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@ -1914,13 +1920,14 @@ again:
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nbd_put(nbd);
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return -EINVAL;
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}
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config = nbd->config = nbd_alloc_config();
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if (!nbd->config) {
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config = nbd_alloc_config();
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if (IS_ERR(config)) {
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mutex_unlock(&nbd->config_lock);
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nbd_put(nbd);
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printk(KERN_ERR "nbd: couldn't allocate config\n");
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return -ENOMEM;
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return PTR_ERR(config);
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}
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nbd->config = config;
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refcount_set(&nbd->config_refs, 1);
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set_bit(NBD_RT_BOUND, &config->runtime_flags);
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@ -2493,6 +2500,9 @@ static void __exit nbd_cleanup(void)
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while (!list_empty(&del_list)) {
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nbd = list_first_entry(&del_list, struct nbd_device, list);
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list_del_init(&nbd->list);
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if (refcount_read(&nbd->config_refs))
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printk(KERN_ERR "nbd: possibly leaking nbd_config (ref %d)\n",
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refcount_read(&nbd->config_refs));
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if (refcount_read(&nbd->refs) != 1)
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printk(KERN_ERR "nbd: possibly leaking a device\n");
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nbd_put(nbd);
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