[PATCH] nvme-tcp: fix crash triggered with a dataless request submission

[Chaitanya Kulkarni]

On 2/10/21 2:10 PM, Sagi Grimberg wrote:
> write-zeros has a bio, but does not have any data buffers associated
> with it. Hence should not initialize the request iter for it (which
> attempts to reference the bi_io_vec (and crash).
> --
>  run blktests nvme/012 at 2021-02-05 21:53:34
>  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] SMP NOPTI
>  CPU: 15 PID: 12069 Comm: kworker/15:2H Tainted: G S        I       5.11.0-rc6+ #1
>  Hardware name: Dell Inc. PowerEdge R640/06NR82, BIOS 2.10.0 11/12/2020
>  Workqueue: kblockd blk_mq_run_work_fn
>  RIP: 0010:nvme_tcp_init_iter+0x7d/0xd0 [nvme_tcp]
>  RSP: 0018:ffffbd084447bd18 EFLAGS: 00010246
>  RAX: 0000000000000000 RBX: ffffa0bba9f3ce80 RCX: 0000000000000000
>  RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000002000000
>  RBP: ffffa0ba8ac6fec0 R08: 0000000002000000 R09: 0000000000000000
>  R10: 0000000002800809 R11: 0000000000000000 R12: 0000000000000000
>  R13: ffffa0bba9f3cf90 R14: 0000000000000000 R15: 0000000000000000
>  FS:  0000000000000000(0000) GS:ffffa0c9ff9c0000(0000) knlGS:0000000000000000
>  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>  CR2: 0000000000000008 CR3: 00000001c9c6c005 CR4: 00000000007706e0
>  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>  PKRU: 55555554
>  Call Trace:
>   nvme_tcp_queue_rq+0xef/0x330 [nvme_tcp]
>   blk_mq_dispatch_rq_list+0x11c/0x7c0
>   ? blk_mq_flush_busy_ctxs+0xf6/0x110
>   __blk_mq_sched_dispatch_requests+0x12b/0x170
>   blk_mq_sched_dispatch_requests+0x30/0x60
>   __blk_mq_run_hw_queue+0x2b/0x60
>   process_one_work+0x1cb/0x360
>   ? process_one_work+0x360/0x360
>   worker_thread+0x30/0x370
>   ? process_one_work+0x360/0x360
>   kthread+0x116/0x130
>   ? kthread_park+0x80/0x80
>   ret_from_fork+0x1f/0x30
> --
>
> Fixes: cb9b870fba3e ("nvme-tcp: fix wrong setting of request iov_iter")
> Reported-by: Yi Zhang <yi.zhang at redhat.com>
> Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
Looks good.

Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni at wdc.com>