Hi,
在 2023/09/28 17:24, Ming Lei 写道:
On Thu, Sep 28, 2023 at 05:06:40PM +0800, Yu Kuai wrote:
Hi,
在 2023/09/28 16:57, Ming Lei 写道:
On Thu, Sep 28, 2023 at 04:55:03PM +0800, Yu Kuai wrote:
Hi,
在 2023/09/28 15:40, Ming Lei 写道:
On Thu, Sep 28, 2023 at 02:03:28PM +0800, Yu Kuai wrote:
Hi,
在 2023/09/28 12:05, Ming Lei 写道:
On Mon, Sep 11, 2023 at 10:33:08AM +0800, linan666@xxxxxxxxxxxxxxx wrote:
From: Li Nan <linan122@xxxxxxxxxx>
If a socket is processing ioctl 'NBD_SET_SOCK', config->socks might be
krealloc in nbd_add_socket(), and a garbage request is received now, a UAF
may occurs.
T1
nbd_ioctl
__nbd_ioctl
nbd_add_socket
blk_mq_freeze_queue
T2
recv_work
nbd_read_reply
sock_xmit
krealloc config->socks
def config->socks
Pass nbd_sock to nbd_read_reply(). And introduce a new function
sock_xmit_recv(), which differs from sock_xmit only in the way it get
socket.
I am wondering why not grab queue usage counter before calling nbd_read_reply()
for avoiding such issue, something like the following change:
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index df1cd0f718b8..09215b605b12 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -837,9 +837,6 @@ static void recv_work(struct work_struct *work)
while (1) {
struct nbd_reply reply;
- if (nbd_read_reply(nbd, args->index, &reply))
- break;
-
/*
* Grab .q_usage_counter so request pool won't go away, then no
* request use-after-free is possible during nbd_handle_reply().
@@ -852,6 +849,9 @@ static void recv_work(struct work_struct *work)
break;
}
This break how nbd works, if there is no reply yet, recv_work() will
wait for reply in:
nbd_read_reply
sock_xmit
sock_recvmsg
After this change, recv_work() will just return if there is no io.
OK, got it, thanks for the input.
But I feel it isn't necessary & fragile to store one extra reference of nsock in
`recv_thread_args`.
Just run a quick look, the only potential UAF on config->socks should be recv_work(),
so you can retrieve the `nsock` reference at the entry of recv_work(),
I don't understand what you mean retrieve the 'nsock', is following what
you expected?
blk_queue_enter() -> prevent concurrent with nbd_add_socket
nsock = config->socks[args->index]
blk_queue_exit()
Yeah, turns out you do understand, :-)
Ok, I was not sure about this blk_queue_enter(). By the way, this
blk_queue_enter() isn't exported, but you can grab ->config_lock
for getting the `nsock`.
remind me of what you did to fix uaf of access queue->mq_hctx[] by
convert the array to xarray.
Maybe it's better to covert config->socks[] to xarray to fix this uaf as
well?
->socks[idx] is needed in nbd fast path, so xarray may not be one good idea
since xarray_load() introduces extra load, especially ->socks[] uaf
should exist in recv_work() very likely. For other cases, the active
block request holds queue usage counter.
Thanks for the explanation, grab 'config_lock' to get 'nsock' in the
begining sounds good to me.
Kuai
Thanks,
Ming
.
