6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Zheng Qixing zhengqixing@huawei.com
[ Upstream commit 1649714b930f9ea6233ce0810ba885999da3b5d4 ]
There is one use-after-free warning when running NBD_CMD_CONNECT and NBD_CLEAR_SOCK:
nbd_genl_connect nbd_alloc_and_init_config // config_refs=1 nbd_start_device // config_refs=2 set NBD_RT_HAS_CONFIG_REF open nbd // config_refs=3 recv_work done // config_refs=2 NBD_CLEAR_SOCK // config_refs=1 close nbd // config_refs=0 refcount_inc -> uaf
------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 24 PID: 1014 at lib/refcount.c:25 refcount_warn_saturate+0x12e/0x290 nbd_genl_connect+0x16d0/0x1ab0 genl_family_rcv_msg_doit+0x1f3/0x310 genl_rcv_msg+0x44a/0x790
The issue can be easily reproduced by adding a small delay before refcount_inc(&nbd->config_refs) in nbd_genl_connect():
mutex_unlock(&nbd->config_lock); if (!ret) { set_bit(NBD_RT_HAS_CONFIG_REF, &config->runtime_flags); + printk("before sleep\n"); + mdelay(5 * 1000); + printk("after sleep\n"); refcount_inc(&nbd->config_refs); nbd_connect_reply(info, nbd->index); }
Fixes: e46c7287b1c2 ("nbd: add a basic netlink interface") Signed-off-by: Zheng Qixing zhengqixing@huawei.com Reviewed-by: Yu Kuai yukuai@fnnas.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/block/nbd.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index e6b756c475cde..958bd115a3417 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -2169,12 +2169,13 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
ret = nbd_start_device(nbd); out: - mutex_unlock(&nbd->config_lock); if (!ret) { set_bit(NBD_RT_HAS_CONFIG_REF, &config->runtime_flags); refcount_inc(&nbd->config_refs); nbd_connect_reply(info, nbd->index); } + mutex_unlock(&nbd->config_lock); + nbd_config_put(nbd); if (put_dev) nbd_put(nbd);