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author | Yu Kuai <yukuai3@huawei.com> | 2022-05-21 15:37:45 +0800 |
---|---|---|
committer | Jens Axboe <axboe@kernel.dk> | 2022-05-27 20:39:33 -0600 |
commit | c55b2b983b0fa012942c3eb16384b2b722caa810 (patch) | |
tree | 2db9540992f04a43cd8a805c4bed5334af88566f /drivers | |
parent | 06c4da89c24e7023ea448cadf8e9daf06a0aae6e (diff) | |
download | linux-c55b2b983b0fa012942c3eb16384b2b722caa810.tar.gz linux-c55b2b983b0fa012942c3eb16384b2b722caa810.tar.bz2 linux-c55b2b983b0fa012942c3eb16384b2b722caa810.zip |
nbd: fix race between nbd_alloc_config() and module removal
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>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/block/nbd.c | 28 |
1 files changed, 19 insertions, 9 deletions
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index a73e853f5833..2ee1e376d5c4 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1518,15 +1518,20 @@ static struct nbd_config *nbd_alloc_config(void) { struct nbd_config *config; + if (!try_module_get(THIS_MODULE)) + return ERR_PTR(-ENODEV); + config = kzalloc(sizeof(struct nbd_config), GFP_NOFS); - if (!config) - return NULL; + if (!config) { + module_put(THIS_MODULE); + return ERR_PTR(-ENOMEM); + } + atomic_set(&config->recv_threads, 0); init_waitqueue_head(&config->recv_wq); init_waitqueue_head(&config->conn_wait); config->blksize_bits = NBD_DEF_BLKSIZE_BITS; atomic_set(&config->live_connections, 0); - try_module_get(THIS_MODULE); return config; } @@ -1553,12 +1558,13 @@ static int nbd_open(struct block_device *bdev, fmode_t mode) mutex_unlock(&nbd->config_lock); goto out; } - config = nbd->config = nbd_alloc_config(); - if (!config) { - ret = -ENOMEM; + config = nbd_alloc_config(); + if (IS_ERR(config)) { + ret = PTR_ERR(config); mutex_unlock(&nbd->config_lock); goto out; } + nbd->config = config; refcount_set(&nbd->config_refs, 1); refcount_inc(&nbd->refs); mutex_unlock(&nbd->config_lock); @@ -1964,13 +1970,14 @@ again: nbd_put(nbd); return -EINVAL; } - config = nbd->config = nbd_alloc_config(); - if (!nbd->config) { + config = nbd_alloc_config(); + if (IS_ERR(config)) { mutex_unlock(&nbd->config_lock); nbd_put(nbd); printk(KERN_ERR "nbd: couldn't allocate config\n"); - return -ENOMEM; + return PTR_ERR(config); } + nbd->config = config; refcount_set(&nbd->config_refs, 1); set_bit(NBD_RT_BOUND, &config->runtime_flags); @@ -2543,6 +2550,9 @@ static void __exit nbd_cleanup(void) while (!list_empty(&del_list)) { nbd = list_first_entry(&del_list, struct nbd_device, list); list_del_init(&nbd->list); + if (refcount_read(&nbd->config_refs)) + printk(KERN_ERR "nbd: possibly leaking nbd_config (ref %d)\n", + refcount_read(&nbd->config_refs)); if (refcount_read(&nbd->refs) != 1) printk(KERN_ERR "nbd: possibly leaking a device\n"); nbd_put(nbd); |