[PATCH -next] nbd: get config_lock before sock_shutdown
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@huaweicloud.com>
---
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 c410cf29fb0c..accbe99ebb7e 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1428,13 +1428,18 @@ static int nbd_start_device_ioctl(struct nbd_device *nbd)
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);
nbd_clear_que(nbd);
}
flush_workqueue(nbd->recv_workq);
- mutex_lock(&nbd->config_lock);
nbd_bdev_reset(nbd);
/* user requested, ignore socket errors */
if (test_bit(NBD_RT_DISCONNECT_REQUESTED, &config->runtime_flags))
--
2.31.1
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