From: Yu Kuai yukuai3@huawei.com

Offering: HULK hulk inclusion category: bugfix bugzilla: 188902

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

There are no functional changes, make the code cleaner and prepare to fix null-ptr-dereference while accessing 'nbd->config'.

Signed-off-by: Yu Kuai yukuai3@huawei.com Signed-off-by: Zhong Jinghua zhongjinghua@huawei.com --- drivers/block/nbd.c | 41 +++++++++++++++++++---------------------- 1 file changed, 19 insertions(+), 22 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 57c4053e957d..b544a301a11f 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1534,17 +1534,20 @@ static int nbd_ioctl(struct block_device *bdev, fmode_t mode, return error; }

-static struct nbd_config *nbd_alloc_config(void) +static int nbd_alloc_and_init_config(struct nbd_device *nbd) { struct nbd_config *config;

+ if (WARN_ON(nbd->config)) + return -EINVAL; + if (!try_module_get(THIS_MODULE)) - return ERR_PTR(-ENODEV); + return -ENODEV;

config = kzalloc(sizeof(struct nbd_config), GFP_NOFS); if (!config) { module_put(THIS_MODULE); - return ERR_PTR(-ENOMEM); + return -ENOMEM; }

atomic_set(&config->recv_threads, 0); @@ -1552,7 +1555,10 @@ static struct nbd_config *nbd_alloc_config(void) init_waitqueue_head(&config->conn_wait); config->blksize = NBD_DEF_BLKSIZE; atomic_set(&config->live_connections, 0); - return config; + nbd->config = config; + refcount_set(&nbd->config_refs, 1); + + return 0; }

static int nbd_open(struct block_device *bdev, fmode_t mode) @@ -1571,21 +1577,17 @@ static int nbd_open(struct block_device *bdev, fmode_t mode) goto out; } if (!refcount_inc_not_zero(&nbd->config_refs)) { - struct nbd_config *config; - mutex_lock(&nbd->config_lock); if (refcount_inc_not_zero(&nbd->config_refs)) { mutex_unlock(&nbd->config_lock); goto out; } - config = nbd_alloc_config(); - if (IS_ERR(config)) { - ret = PTR_ERR(config); + ret = nbd_alloc_and_init_config(nbd); + if (ret) { 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); set_bit(GD_NEED_PART_SCAN, &bdev->bd_disk->state); @@ -2006,22 +2008,17 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info) printk(KERN_ERR "nbd: nbd%d already in use\n", index); return -EBUSY; } - if (WARN_ON(nbd->config)) { - mutex_unlock(&nbd->config_lock); - nbd_put(nbd); - return -EINVAL; - } - config = nbd_alloc_config(); - if (IS_ERR(config)) { + + ret = nbd_alloc_and_init_config(nbd); + if (ret) { mutex_unlock(&nbd->config_lock); nbd_put(nbd); printk(KERN_ERR "nbd: couldn't allocate config\n"); - return PTR_ERR(config); + return ret; } - nbd->config = config; - refcount_set(&nbd->config_refs, 1); - set_bit(NBD_RT_BOUND, &config->runtime_flags);

+ config = nbd->config; + set_bit(NBD_RT_BOUND, &config->runtime_flags); ret = nbd_genl_size_set(info, nbd); if (ret) goto out;

From: Yu Kuai yukuai3@huawei.com

Offering: HULK hulk inclusion category: bugfix bugzilla: 188902, https://gitee.com/openeuler/kernel/issues/I7EENU

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

nbd->config = config and refcount_set(&nbd->config_refs, 1) in nbd_genl_connect may be out of order, causing config_refs to be set to 1 first, and then nbd_open accessing nbd->config reports a null pointer reference. T1 T2 vfs_open do_dentry_open blkdev_open blkdev_get __blkdev_get nbd_open nbd_get_config_unlocked genl_rcv_msg genl_family_rcv_msg genl_family_rcv_msg_doit nbd_genl_connect nbd_alloc_and_init_config // out of order execution refcount_set(&nbd->config_refs, 1); // 2 nbd->config // null point nbd->config = config; // 1

Fix it by adding a cpu memory barrier to guarantee sequential execution.

Signed-off-by: Yu Kuai yukuai3@huawei.com Signed-off-by: Zhong Jinghua zhongjinghua@huawei.com --- drivers/block/nbd.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index d85cb372f292..c073d6c1576d 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -391,8 +391,16 @@ static u32 req_to_nbd_cmd_type(struct request *req)

static struct nbd_config *nbd_get_config_unlocked(struct nbd_device *nbd) { - if (refcount_inc_not_zero(&nbd->config_refs)) + if (refcount_inc_not_zero(&nbd->config_refs)) { + /* + * Add smp_mb__after_atomic to ensure that reading nbd->config_refs + * and reading nbd->config is ordered. The pair is the barrier in + * nbd_alloc_and_init_config(), avoid nbd->config_refs is set + * before nbd->config. + */ + smp_mb__after_atomic(); return nbd->config; + }

return NULL; } @@ -1563,7 +1571,15 @@ static int nbd_alloc_and_init_config(struct nbd_device *nbd) init_waitqueue_head(&config->conn_wait); config->blksize = NBD_DEF_BLKSIZE; atomic_set(&config->live_connections, 0); + nbd->config = config; + /* + * Order refcount_set(&nbd->config_refs, 1) and nbd->config assignment, + * its pair is the barrier in nbd_get_config_unlocked(). + * So nbd_get_config_unlocked() won't see nbd->config as null after + * refcount_inc_not_zero() succeed. + */ + smp_mb__before_atomic(); refcount_set(&nbd->config_refs, 1);

return 0;