maillist inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IBGB8Q CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/commit... ---------------------------------------- Following process can cause nbd_config UAF: 1) grab nbd_config temporarily; 2) nbd_genl_disconnect() flush all recv_work() and release the initial reference: nbd_genl_disconnect nbd_disconnect_and_put nbd_disconnect flush_workqueue(nbd->recv_workq) if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, ...)) nbd_config_put -> due to step 1), reference is still not zero 3) nbd_genl_reconfigure() queue recv_work() again; nbd_genl_reconfigure config = nbd_get_config_unlocked(nbd) if (!config) -> succeed if (!test_bit(NBD_RT_BOUND, ...)) -> succeed nbd_reconnect_socket queue_work(nbd->recv_workq, &args->work) 4) step 1) release the reference; 5) Finially, recv_work() will trigger UAF: recv_work nbd_config_put(nbd) -> nbd_config is freed atomic_dec(&config->recv_threads) -> UAF Fix the problem by clearing NBD_RT_BOUND in nbd_genl_disconnect(), so that nbd_genl_reconfigure() will fail. Fixes: b7aa3d39385d ("nbd: add a reconfigure netlink command") Reported-by: syzbot+6b0df248918b92c33e6a@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/675bfb65.050a0220.1a2d0d.0006.GAE@google.com/ Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20250103092859.3574648-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk> --- drivers/block/nbd.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 9d413c4fd64c..fbc4cdb5a5b9 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -2083,6 +2083,7 @@ static void nbd_disconnect_and_put(struct nbd_device *nbd) mutex_lock(&nbd->config_lock); nbd_disconnect(nbd); nbd_clear_sock(nbd); + clear_bit(NBD_RT_BOUND, &nbd->config->runtime_flags); mutex_unlock(&nbd->config_lock); /* * Make sure recv thread has finished, so it does not drop the last -- 2.39.2