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

From: Ding Hui
Date: Tue Dec 13 2022 - 04:05:53 EST

On 2022/12/13 1:00, Mike Christie wrote:
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.


Hi Wenchao and Mike,

Thanks for your work, I am looking forward to it.

--
Thanks,
- Ding Hui