[PATCH] nvmet-tcp: finish receiving before send back response if nvmet_req_init() failed.

[Hou Pu]

When receiving a pdu, if nvmet_req_init() failed (for example a ns is
not found), the queue->rcv_state could be moved to NVMET_TCP_RECV_DATA
by nvmet_tcp_handle_req_failure(). We should return 0 here to continue
to consume the possible remaining inline write out data in
nvmet_tcp_try_recv_one(). Otherwise, the response to this request would
be sent and iov would be freed. Next time in nvmet_tcp_try_recv_one(),
we would go to the receiving data phase and the iov is used again.

A panic happend with a 5.4 kernel installed as below:

[  169.906573] nvmet_tcp: failed cmd 0000000027717054 id 106 opcode 1, data_len: 1024
[  169.908131] general protection fault: 0000 [#1] SMP NOPTI
[  169.908884] CPU: 0 PID: 122 Comm: kworker/0:1H Kdump: loaded Tainted: G           OE [...]
[  169.910328] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), [...]
[  169.911943] Workqueue: nvmet_tcp_wq nvmet_tcp_io_work [nvmet_tcp]
[  169.912815] RIP: 0010:__memcpy+0x12/0x20
[  169.913393] Code: e3 97 ff 0f 31 48 c1 e2 20 48 09 d0 48 31 c3 e9 79 ff [...]
[  169.915819] RSP: 0018:ffffc9000026bbc8 EFLAGS: 00010246
[  169.916547] RAX: ebf4958c4fda661b RBX: ffff888119613096 RCX: 0000000000000080
[  169.917511] RDX: 0000000000000000 RSI: ffff888119613096 RDI: ebf4958c4fda661b
[  169.918469] RBP: 0000000000000400 R08: 0000000000000000 R09: 0000000000000400
[  169.919435] R10: 0000000000000000 R11: 000000000000003e R12: ffff888114244068
[  169.920398] R13: 0000000000000400 R14: 0000000000000400 R15: ffff888118c37cb0
[  169.921378] FS:  0000000000000000(0000) GS:ffff88813fc00000(0000) knlGS:0000000000000000
[  169.922473] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  169.923269] CR2: 0000555eb19943e0 CR3: 00000001186fc000 CR4: 00000000000006f0
[  169.924245] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  169.925214] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  169.926184] Call Trace:
[  169.926569]  _copy_to_iter+0x26f/0x440
[  169.927112]  ? __check_object_size+0x70/0x230
[  169.927724]  __skb_datagram_iter+0x15a/0x290
[  169.928327]  ? skb_kill_datagram+0x60/0x60
[  169.928921]  skb_copy_datagram_iter+0x3b/0x90
[  169.929545]  tcp_recvmsg+0x759/0xc50
[  169.930081]  ? ksoftirqd_running+0x2c/0x30
[  169.930668]  ? free_unref_page_commit+0x95/0x120
[  169.931331]  inet_recvmsg+0x55/0xc0
[  169.931834]  nvmet_tcp_io_work+0x685/0xb23 [nvmet_tcp]
[  169.932549]  process_one_work+0x18c/0x370
[  169.933118]  worker_thread+0x4f/0x3b0
[  169.933654]  ? rescuer_thread+0x340/0x340
[  169.934223]  kthread+0xf6/0x130
[  169.934682]  ? kthread_create_worker_on_cpu+0x70/0x70
[  169.935393]  ret_from_fork+0x1f/0x30

Cc: <stable at vger.kernel.org> # 5.0
Signed-off-by: Hou Pu <houpu.main at gmail.com>
---
 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 8b0485ada315..da1c667e21ba 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -961,7 +961,7 @@ static int nvmet_tcp_done_recv_pdu(struct nvmet_tcp_queue *queue)
 			le32_to_cpu(req->cmd->common.dptr.sgl.length));
 
 		nvmet_tcp_handle_req_failure(queue, queue->cmd, req);
-		return -EAGAIN;
+		return 0;
 	}
 
 	ret = nvmet_tcp_map_data(queue->cmd);
-- 
2.28.0