Re: [PATCH] nvmet-tcp: Fix NULL pointer dereference during release

[Sagi Grimberg]

On 8/30/22 11:36, zhenwei pi wrote:
> nvmet-tcp frees CMD buffers in nvmet_tcp_uninit_data_in_cmds(),
> and waits the inflight IO requests in nvmet_sq_destroy(). During wait
> the inflight IO requests, the callback nvmet_tcp_queue_response()
> is called from backend after IO complete, this leads a typical
> Use-After-Free issue like this:
>
>   BUG: kernel NULL pointer dereference, address: 0000000000000008
>   #PF: supervisor read access in kernel mode
>   #PF: error_code(0x0000) - not-present page
>   PGD 0 P4D 0
>   Oops: 0000 [#1] PREEMPT SMP NOPTI
>   CPU: 14 PID: 207 Comm: kworker/14:1H Kdump: loaded Tainted: G            E      6.0.0-rc2.bm.1-amd64 #12
>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
>   Workqueue: nvmet_tcp_wq nvmet_tcp_io_work [nvmet_tcp]
>   RIP: 0010:shash_ahash_digest+0x2b/0x110

This data access is specific to data-digest, because at this point there
is no way for the data to be sent down the wire as the socket is shut
down.

>   Code: 1f 44 00 00 41 57 41 56 41 55 41 54 55 48 89 fd 53 48 89 f3 48 83 ec 08 44 8b 67 30 45 85 e4 74 1c 48 8b 57 38 b8 00 10 00 00 <44> 8b 7a 08 44 29 f8 39 42 0c 0f 46 42 0c 41 39 c4 76 43 48 8b 03
>   RSP: 0018:ffffc900006e3dd8 EFLAGS: 00010206
>   RAX: 0000000000001000 RBX: ffff888104ac1650 RCX: 0000000000000000
>   RDX: 0000000000000000 RSI: ffff888104ac1650 RDI: ffff888104ac1600
>   RBP: ffff888104ac1600 R08: ffff8881073980c8 R09: ffff8881057798b8
>   R10: 8080808080808080 R11: 0000000000000000 R12: 0000000000001000
>   R13: 0000000000000000 R14: ffff88810601a1cc R15: ffff888107398000
>   FS:  0000000000000000(0000) GS:ffff88823fd80000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 0000000000000008 CR3: 000000010a8e8000 CR4: 0000000000350ee0
>   Call Trace:
>    <TASK>
>    nvmet_tcp_io_work+0xa1c/0xb1c [nvmet_tcp]
>    ? __switch_to+0x106/0x420
>    process_one_work+0x1ae/0x380
>    ? process_one_work+0x380/0x380
>    worker_thread+0x30/0x360
>    ? process_one_work+0x380/0x380
>    kthread+0xe6/0x110
>    ? kthread_complete_and_exit+0x20/0x20
>    ret_from_fork+0x1f/0x30
>
> To fix this issue, free CMD buffers until all the inflight IO
> complete.
>
> Signed-off-by: zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
> ---
>   drivers/nvme/target/tcp.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
> index dc3b4dc8fe08..2325246e3b4d 100644
> --- a/drivers/nvme/target/tcp.c
> +++ b/drivers/nvme/target/tcp.c
> @@ -1449,8 +1449,8 @@ static void nvmet_tcp_release_queue_work(struct work_struct *w)
>   	/* stop accepting incoming data */
>   	queue->rcv_state = NVMET_TCP_RECV_ERR;
>   
> -	nvmet_tcp_uninit_data_in_cmds(queue);
>   	nvmet_sq_destroy(&queue->nvme_sq);
> +	nvmet_tcp_uninit_data_in_cmds(queue);

We still need to uninit the nvmet request so nvmet_sq_destroy()
can complete. Please separate nvmet_tcp_uninit_data_in_cmds to
uninit and free potions, only the free should go after the sq_destroy.