From: Josef Bacik josef@toxicpanda.com
stable inclusion from linux-4.19.173 commit 424838c0f727f1d11ce2ccaabba96f4346c03906 CVE: CVE-2021-3348
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commit b98e762e3d71e893b221f871825dc64694cfb258 upstream.
When setting up a device, we can krealloc the config->socks array to add new sockets to the configuration. However if we happen to get a IO request in at this point even though we aren't setup we could hit a UAF, as we deref config->socks without any locking, assuming that the configuration was setup already and that ->socks is safe to access it as we have a reference on the configuration.
But there's nothing really preventing IO from occurring at this point of the device setup, we don't want to incur the overhead of a lock to access ->socks when it will never change while the device is running. To fix this UAF scenario simply freeze the queue if we are adding sockets. This will protect us from this particular case without adding any additional overhead for the normal running case.
Cc: stable@vger.kernel.org Signed-off-by: Josef Bacik josef@toxicpanda.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com Reviewed-by: Xiu Jianfeng xiujianfeng@huawei.com Reviewed-by: Yufen Yu yuyufen@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- drivers/block/nbd.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 97fcb040056c..d0c4b5bcf874 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -984,6 +984,12 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg, if (!sock) return err;
+ /* + * We need to make sure we don't get any errant requests while we're + * reallocating the ->socks array. + */ + blk_mq_freeze_queue(nbd->disk->queue); + if (!netlink && !nbd->task_setup && !test_bit(NBD_RT_BOUND, &config->runtime_flags)) nbd->task_setup = current; @@ -1022,10 +1028,12 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg, nsock->cookie = 0; socks[config->num_connections++] = nsock; atomic_inc(&config->live_connections); + blk_mq_unfreeze_queue(nbd->disk->queue);
return 0;
put_socket: + blk_mq_unfreeze_queue(nbd->disk->queue); sockfd_put(sock); return err; }