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

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From: Xiubo Li <lixiubo@xxxxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxx>
Tested-by: Damien Le Moal <damien.lemoal@xxxxxxx>
Signed-off-by: Xiubo Li <lixiubo@xxxxxxxxxxxxxxxxxxxx>
---
  drivers/target/target_core_user.c | 12 +++++-------
  1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 2f1fa92..3b25ef3 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c

Nice! This has fixed our long standing issue with not being able to boot with the global data area support on power.

Tested-by: Bryant G. Ly <bryantly@xxxxxxxxxxxxxxxxxx>

-Bryant





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