Re: [PATCHv2] tcmu: Fix possbile memory leak when recalculating the cmd base size

[Mike Christie <mchristi@redhat.com>]

On 07/11/2017 04:59 AM, lixiubo@cmss.chinamobile.com wrote:
> From: Xiubo Li <lixiubo@cmss.chinamobile.com>
> 
> For all the entries allocated from the ring cmd area, the memory is
> something like the stack memory, which will always reserve the old
> data, so the entry->req.iov_bidi_cnt maybe none zero.
> 
> On some environments, the crash could be reporduce very easy and some
> not. The following is the crash core trace:
> 
> [  240.143969] CPU: 0 PID: 1285 Comm: iscsi_trx Not tainted
> 4.12.0-rc1+ #3
> [  240.150607] Hardware name: ASUS All Series/H87-PRO, BIOS 2104
> 10/28/2014
> [  240.157331] task: ffff8807de4f5800 task.stack:
> ffffc900047dc000
> [  240.163270] RIP: 0010:memcpy_erms+0x6/0x10
> [  240.167377] RSP: 0018:ffffc900047dfc68 EFLAGS: 00010202
> [  240.172621] RAX: ffffc9065db85540 RBX: ffff8807f7980000 RCX:
> 0000000000000010
> [  240.179771] RDX: 0000000000000010 RSI: ffff8807de574fe0 RDI:
> ffffc9065db85540
> [  240.186930] RBP: ffffc900047dfd30 R08: ffff8807de41b000 R09:
> 0000000000000000
> [  240.194088] R10: 0000000000000040 R11: ffff8807e9b726f0 R12:
> 00000006565726b0
> [  240.201246] R13: ffffc90007612ea0 R14: 000000065657d540 R15:
> 0000000000000000
> [  240.208397] FS:  0000000000000000(0000)
> GS:ffff88081fa00000(0000)
> knlGS:0000000000000000
> [  240.216510] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  240.222280] CR2: ffffc9065db85540 CR3: 0000000001c0f000 CR4:
> 00000000001406f0
> [  240.229430] Call Trace:
> [  240.231887]  ? tcmu_queue_cmd+0x83c/0xa80
> [  240.235916]  ? target_check_reservation+0xcd/0x6f0
> [  240.240725]  __target_execute_cmd+0x27/0xa0
> [  240.244918]  target_execute_cmd+0x232/0x2c0
> [  240.249124]  ? __local_bh_enable_ip+0x64/0xa0
> [  240.253499]  iscsit_execute_cmd+0x20d/0x270
> [  240.257693]  iscsit_sequence_cmd+0x110/0x190
> [  240.261985]  iscsit_get_rx_pdu+0x360/0xc80
> [  240.267565]  ? iscsi_target_rx_thread+0x54/0xd0
> [  240.273571]  iscsi_target_rx_thread+0x9a/0xd0
> [  240.279413]  kthread+0x113/0x150
> [  240.284120]  ? iscsi_target_tx_thread+0x1e0/0x1e0
> [  240.290297]  ? kthread_create_on_node+0x40/0x40
> [  240.296297]  ret_from_fork+0x2e/0x40
> [  240.301332] Code: 90 90 90 90 90 eb 1e 0f 1f 00 48 89 f8 48
> 89 d1 48
> c1 e9 03 83 e2 07 f3 48 a5 89 d1 f3 a4 c3 66 0f 1f 44 00 00 48
> 89 f8 48
> 89 d1 <f3> a4 c3 0f 1f 80 00 00 00 00 48 89 f8 48 83 fa 20 72 7e
> 40 38
> [  240.321751] RIP: memcpy_erms+0x6/0x10 RSP: ffffc900047dfc68
> [  240.328838] CR2: ffffc9065db85540
> [  240.333667] ---[ end trace b7e5354cfb54d08b ]---
> 
> To fix this, just memset all the entry memory before using it, and
> also to be more readable we adjust the bidi code.
> 
> Fixed: fe25cc34795(tcmu: Recalculate the tcmu_cmd size to save cmd area
> 		memories)
> Reported-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com>
> Tested-by: Damien Le Moal <damien.lemoal@wdc.com>
> Signed-off-by: Xiubo Li <lixiubo@cmss.chinamobile.com>
> ---

Nice. Thanks.

Reviewed-by: Mike Christie <mchristi@redhat.com>