linux-kernel - Re: [PATCH v4 1/1] nvmet-tcp: Fix NULL pointer dereference during release

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Message-ID: <b3362f45-fcb5-4ace-16e5-97a77ca3ca10@grimberg.me>
Date:   Wed, 14 Sep 2022 13:44:40 +0300
From:   Sagi Grimberg <sagi@...mberg.me>
To:     zhenwei pi <pizhenwei@...edance.com>, hch@....de
Cc:     kch@...dia.com, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org, fmdefrancesco@...il.com
Subject: Re: [PATCH v4 1/1] nvmet-tcp: Fix NULL pointer dereference during
 release



On 9/13/22 04:42, 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
>   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
> 
> Suggested by Sagi, separate nvmet_tcp_uninit_data_in_cmds() into two
> steps:
>    uninit data in cmds                  <- new step 1
>    nvmet_sq_destroy();
>    cancel_work_sync(&queue->io_work);
>    free CMD buffers                     <- new step 2
> 
> Signed-off-by: zhenwei pi <pizhenwei@...edance.com>
> ---
>   drivers/nvme/target/tcp.c | 20 ++++++++++++++++++--
>   1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
> index a3694a32f6d5..3ac9750b41ad 100644
> --- a/drivers/nvme/target/tcp.c
> +++ b/drivers/nvme/target/tcp.c
> @@ -1423,14 +1423,29 @@ static void nvmet_tcp_uninit_data_in_cmds(struct nvmet_tcp_queue *queue)
>   	for (i = 0; i < queue->nr_cmds; i++, cmd++) {
>   		if (nvmet_tcp_need_data_in(cmd))
>   			nvmet_req_uninit(&cmd->req);
> +	}
> +
> +	if (!queue->nr_cmds && nvmet_tcp_need_data_in(&queue->connect)) {
> +		/* failed in connect */
> +		nvmet_req_uninit(&queue->connect.req);
> +	}
> +}
>   
> +static void nvmet_tcp_free_cmd_data_in_buffers(struct nvmet_tcp_queue *queue)
> +{
> +	struct nvmet_tcp_cmd *cmd = queue->cmds;
> +	int i;
> +
> +	for (i = 0; i < queue->nr_cmds; i++, cmd++) {
> +		if (!nvmet_tcp_need_data_in(cmd))
> +			continue;
>   		nvmet_tcp_unmap_pdu_iovec(cmd);

This will cause a merge conflict, because nvme-6.1
nvmet_tcp_unmap_pdu_iovec does no longer exist.

Other than that, looks fine to me,
Reviewed-by: Sagi Grimberg <sagi@...mberg.me>