Messages in this thread | | | Subject | Re: [PATCH] nbd: pass nbd_sock to nbd_read_reply() instead of index | From | Yu Kuai <> | Date | Thu, 28 Sep 2023 16:55:03 +0800 |
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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@huaweicloud.com wrote: >>>> From: Li Nan <linan122@huawei.com> >>>> >>>> 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()
while (1) { ... // pass nsock to nbd_read_reply() and nbd_handle_reply() }
> and just pass it(local variable) to nbd_read_reply() and nbd_handle_reply() > since `nsock` won't be freed. > > > Thanks, > Ming > > . >
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