From: Zhong Jinghua <zhongjinghua@huaweicloud.com> Offering: HULK hulk inclusion category: bugfix bugzilla: 188799, https://gitee.com/openeuler/kernel/issues/I79QWO CVE: NA ---------------------------------------- Config->socks in sock_shutdown may trigger a UAF problem. The reason is that sock_shutdown does not hold the config_lock, so that nbd_ioctl can release config->socks at this time. T0: NBD_SET_SOCK T1: NBD_DO_IT T0 T1 nbd_ioctl mutex_lock(&nbd->config_lock) // get lock __nbd_ioctl nbd_start_device_ioctl nbd_start_device mutex_unlock(&nbd->config_lock) // relase lock wait_event_interruptible (kill, enter sock_shutdown) sock_shutdown nbd_ioctl mutex_lock(&nbd->config_lock) // get lock __nbd_ioctl nbd_add_socket krealloc kfree(p) //config->socks is NULL nbd_sock *nsock = config->socks // error Fix it by moving config_lock up before sock_shutdown. Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com> --- v2: adapt drivers/block/nbd.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index ebcdb6025be3..ba98fdaaa35a 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1406,11 +1406,16 @@ static int nbd_start_device_ioctl(struct nbd_device *nbd, struct block_device *b mutex_unlock(&nbd->config_lock); ret = wait_event_interruptible(config->recv_wq, atomic_read(&config->recv_threads) == 0); + + /* + * recv_work in flush_workqueue will not get this lock, because nbd_open + * will hold nbd->config_refs + */ + mutex_lock(&nbd->config_lock); if (ret) sock_shutdown(nbd); flush_workqueue(nbd->recv_workq); - mutex_lock(&nbd->config_lock); nbd_bdev_reset(bdev); /* user requested, ignore socket errors */ if (test_bit(NBD_RT_DISCONNECT_REQUESTED, &config->runtime_flags)) -- 2.31.1