Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Ding Hui <dinghui@sangfor.com.cn>
To:     lduncan@suse.com, cleech@redhat.com, michael.christie@oracle.com,
        jejb@linux.ibm.com, martin.petersen@oracle.com,
        open-iscsi@googlegroups.com, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     Ding Hui <dinghui@sangfor.com.cn>
Subject: [PATCH] scsi: iscsi_tcp: Fix UAF when access shost attr during session logout
Date:   Fri,  9 Dec 2022 16:22:47 +0800
Message-Id: <20221209082247.6330-1-dinghui@sangfor.com.cn>
Precedence: bulk

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.

Signed-off-by: Ding Hui <dinghui@sangfor.com.cn>
---
 drivers/scsi/iscsi_tcp.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 5fb1f364e815..752ef9ccd715 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -959,6 +959,8 @@ iscsi_sw_tcp_session_create(struct iscsi_endpoint *ep, uint16_t cmds_max,
 		goto remove_host;
 	session = cls_session->dd_data;
 	tcp_sw_host = iscsi_host_priv(shost);
+	/* hold refcount for tcp_sw_host */
+	get_device(&cls_session->dev);
 	tcp_sw_host->session = session;
 
 	if (iscsi_tcp_r2tpool_alloc(session))
@@ -966,6 +968,7 @@ iscsi_sw_tcp_session_create(struct iscsi_endpoint *ep, uint16_t cmds_max,
 	return cls_session;
 
 remove_session:
+	put_device(&cls_session->dev);
 	iscsi_session_teardown(cls_session);
 remove_host:
 	iscsi_host_remove(shost, false);
@@ -978,6 +981,7 @@ static void iscsi_sw_tcp_session_destroy(struct iscsi_cls_session *cls_session)
 {
 	struct Scsi_Host *shost = iscsi_session_to_shost(cls_session);
 	struct iscsi_session *session = cls_session->dd_data;
+	struct iscsi_sw_tcp_host *tcp_sw_host = iscsi_host_priv(shost);
 
 	if (WARN_ON_ONCE(session->leadconn))
 		return;
@@ -986,6 +990,10 @@ static void iscsi_sw_tcp_session_destroy(struct iscsi_cls_session *cls_session)
 	iscsi_session_teardown(cls_session);
 
 	iscsi_host_remove(shost, false);
+
+	tcp_sw_host->session = NULL;
+	put_device(&cls_session->dev);
+
 	iscsi_host_free(shost);
 }
 
-- 
2.17.1