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

From: Mike Christie
Date: Mon Dec 12 2022 - 12:00:53 EST

On 12/11/22 8:32 AM, Wenchao Hao wrote:
> On Sun, Dec 11, 2022 at 6:07 AM Mike Christie
> <michael.christie@xxxxxxxxxx> 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@xxxxxxxxxx/
>
> 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.