Re: [PATCH] nbd: defer config unlock in nbd_genl_connect
在 2025/11/10 20:49, Zheng Qixing 写道:
> 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>
> ---
> drivers/block/nbd.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
LGTM
Reviewed-by: Yu Kuai <yukuai@fnnas.com>
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