linux-kernel - Re: [PATCH] scsi: iscsi_tcp: Fix UAF when access shost attr during session logout

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Date:   Mon, 12 Dec 2022 11:00:25 -0600
From:   Mike Christie <michael.christie@...cle.com>
To:     Wenchao Hao <haowenchao22@...il.com>
Cc:     Ding Hui <dinghui@...gfor.com.cn>, lduncan@...e.com,
        cleech@...hat.com, jejb@...ux.ibm.com, martin.petersen@...cle.com,
        open-iscsi@...glegroups.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: iscsi_tcp: Fix UAF when access shost attr during
 session logout

On 12/11/22 8:32 AM, Wenchao Hao wrote:
> On Sun, Dec 11, 2022 at 6:07 AM Mike Christie
> <michael.christie@...cle.com> wrote:
>>
>> On 12/9/22 2:22 AM, Ding Hui wrote:
>>> During iscsi session logout, if another task accessing shost ipaddress
>>> attr at this time, we can get a KASAN UAF report like this:
>>>
>>> [  276.941685] ==================================================================
>>> [  276.942144] BUG: KASAN: use-after-free in _raw_spin_lock_bh+0x78/0xe0
>>> [  276.942535] Write of size 4 at addr ffff8881053b45b8 by task cat/4088
>>> [  276.943511] CPU: 2 PID: 4088 Comm: cat Tainted: G            E      6.1.0-rc8+ #3
>>> [  276.943997] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020
>>> [  276.944470] Call Trace:
>>> [  276.944943]  <TASK>
>>> [  276.945397]  dump_stack_lvl+0x34/0x48
>>> [  276.945887]  print_address_description.constprop.0+0x86/0x1e7
>>> [  276.946421]  print_report+0x36/0x4f
>>> [  276.947358]  kasan_report+0xad/0x130
>>> [  276.948234]  kasan_check_range+0x35/0x1c0
>>> [  276.948674]  _raw_spin_lock_bh+0x78/0xe0
>>> [  276.949989]  iscsi_sw_tcp_host_get_param+0xad/0x2e0 [iscsi_tcp]
>>> [  276.951765]  show_host_param_ISCSI_HOST_PARAM_IPADDRESS+0xe9/0x130 [scsi_transport_iscsi]
>>> [  276.952185]  dev_attr_show+0x3f/0x80
>>> [  276.953005]  sysfs_kf_seq_show+0x1fb/0x3e0
>>> [  276.953401]  seq_read_iter+0x402/0x1020
>>> [  276.954260]  vfs_read+0x532/0x7b0
>>> [  276.955113]  ksys_read+0xed/0x1c0
>>> [  276.955952]  do_syscall_64+0x38/0x90
>>> [  276.956347]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>>> [  276.956769] RIP: 0033:0x7f5d3a679222
>>> [  276.957161] Code: c0 e9 b2 fe ff ff 50 48 8d 3d 32 c0 0b 00 e8 a5 fe 01 00 0f 1f 44 00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 0f 05 <48> 3d 00 f0 ff ff 77 56 c3 0f 1f 44 00 00 48 83 ec 28 48 89 54 24
>>> [  276.958009] RSP: 002b:00007ffc864d16a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
>>> [  276.958431] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f5d3a679222
>>> [  276.958857] RDX: 0000000000020000 RSI: 00007f5d3a4fe000 RDI: 0000000000000003
>>> [  276.959281] RBP: 00007f5d3a4fe000 R08: 00000000ffffffff R09: 0000000000000000
>>> [  276.959682] R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000020000
>>> [  276.960126] R13: 0000000000000003 R14: 0000000000000000 R15: 0000557a26dada58
>>> [  276.960536]  </TASK>
>>> [  276.961357] Allocated by task 2209:
>>> [  276.961756]  kasan_save_stack+0x1e/0x40
>>> [  276.962170]  kasan_set_track+0x21/0x30
>>> [  276.962557]  __kasan_kmalloc+0x7e/0x90
>>> [  276.962923]  __kmalloc+0x5b/0x140
>>> [  276.963308]  iscsi_alloc_session+0x28/0x840 [scsi_transport_iscsi]
>>> [  276.963712]  iscsi_session_setup+0xda/0xba0 [libiscsi]
>>> [  276.964078]  iscsi_sw_tcp_session_create+0x1fd/0x330 [iscsi_tcp]
>>> [  276.964431]  iscsi_if_create_session.isra.0+0x50/0x260 [scsi_transport_iscsi]
>>> [  276.964793]  iscsi_if_recv_msg+0xc5a/0x2660 [scsi_transport_iscsi]
>>> [  276.965153]  iscsi_if_rx+0x198/0x4b0 [scsi_transport_iscsi]
>>> [  276.965546]  netlink_unicast+0x4d5/0x7b0
>>> [  276.965905]  netlink_sendmsg+0x78d/0xc30
>>> [  276.966236]  sock_sendmsg+0xe5/0x120
>>> [  276.966576]  ____sys_sendmsg+0x5fe/0x860
>>> [  276.966923]  ___sys_sendmsg+0xe0/0x170
>>> [  276.967300]  __sys_sendmsg+0xc8/0x170
>>> [  276.967666]  do_syscall_64+0x38/0x90
>>> [  276.968028]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>>> [  276.968773] Freed by task 2209:
>>> [  276.969111]  kasan_save_stack+0x1e/0x40
>>> [  276.969449]  kasan_set_track+0x21/0x30
>>> [  276.969789]  kasan_save_free_info+0x2a/0x50
>>> [  276.970146]  __kasan_slab_free+0x106/0x190
>>> [  276.970470]  __kmem_cache_free+0x133/0x270
>>> [  276.970816]  device_release+0x98/0x210
>>> [  276.971145]  kobject_cleanup+0x101/0x360
>>> [  276.971462]  iscsi_session_teardown+0x3fb/0x530 [libiscsi]
>>> [  276.971775]  iscsi_sw_tcp_session_destroy+0xd8/0x130 [iscsi_tcp]
>>> [  276.972143]  iscsi_if_recv_msg+0x1bf1/0x2660 [scsi_transport_iscsi]
>>> [  276.972485]  iscsi_if_rx+0x198/0x4b0 [scsi_transport_iscsi]
>>> [  276.972808]  netlink_unicast+0x4d5/0x7b0
>>> [  276.973201]  netlink_sendmsg+0x78d/0xc30
>>> [  276.973544]  sock_sendmsg+0xe5/0x120
>>> [  276.973864]  ____sys_sendmsg+0x5fe/0x860
>>> [  276.974248]  ___sys_sendmsg+0xe0/0x170
>>> [  276.974583]  __sys_sendmsg+0xc8/0x170
>>> [  276.974891]  do_syscall_64+0x38/0x90
>>> [  276.975216]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>>>
>>> We can easily reproduce by two tasks:
>>> 1. while :; do iscsiadm -m node --login; iscsiadm -m node --logout; done
>>> 2. while :; do cat /sys/devices/platform/host*/iscsi_host/host*/ipaddress; done
>>>
>>>             iscsid                |        cat
>>> ----------------------------------+-------------------------------------------------
>>> |- iscsi_sw_tcp_session_destroy   |
>>>   |- iscsi_session_teardown       |
>>>     |- device_release             |
>>>       |- iscsi_session_release    |  |- dev_attr_show
>>>         |- kfree                  |    |- show_host_param_ISCSI_HOST_PARAM_IPADDRESS
>>>                                   |      |- iscsi_sw_tcp_host_get_param
>>>                                   |        |- r/w tcp_sw_host->session (UAF)
>>>   |- iscsi_host_remove            |
>>>   |- iscsi_host_free              |
>>>
>>> Since shost hold a pointer to session which is belong to cls_session by its
>>> priv tcp_sw_host, so we should get a ref of cls_session, and after
>>> iscsi_host_remove() the sysfs is cleared, then we can drop the ref.
>>>
>>
>> Nice bug report and thanks for the patch. I think though we should just
>> split the removal from the freeing. The removal will wait on users
>> accessing sysfs files for us, so once they return we know we can just
>> free things.
>>
>> Something like this:
>>
>>
> 
> Hi, dinghui and Mike, I submitted patches to fix this issue one year
> ago. But I missed Mike's
> reply because I was new to the community, so the patches did not keep on.
> 
> https://lore.kernel.org/linux-scsi/20210407012450.97754-1-haowenchao@huawei.com/
> 
> Because of my negligence, this bug has been discovered so far, and I
> apologize for this.

Ah yeah, I remember that now. Don't worry about it. It was also my fault
for not pinging you.

I'll fix up my patches into a proper patchset and submit.