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

[Ding Hui]

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 <din...@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

[Mike Christie]

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:


diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 5fb1f364e815..751e4b19798b 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -982,10 +982,12 @@ static void iscsi_sw_tcp_session_destroy(struct iscsi_cls_session *cls_session)
if (WARN_ON_ONCE(session->leadconn))
return;

+ iscsi_session_remove(cls_session);
+ iscsi_host_remove(shost, false);
+
iscsi_tcp_r2tpool_free(cls_session->dd_data);
- iscsi_session_teardown(cls_session);

- iscsi_host_remove(shost, false);
+ iscsi_session_free(cls_session);
iscsi_host_free(shost);
}

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index ef2fc860257e..235957de1164 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -3104,17 +3104,27 @@ iscsi_session_setup(struct iscsi_transport *iscsit, struct Scsi_Host *shost,
}
EXPORT_SYMBOL_GPL(iscsi_session_setup);

-/**
- * iscsi_session_teardown - destroy session, host, and cls_session
- * @cls_session: iscsi session
+/*
+ * issi_session_remove - Remove session from iSCSI class.
*/
-void iscsi_session_teardown(struct iscsi_cls_session *cls_session)
+void iscsi_session_remove(struct iscsi_cls_session *cls_session)
{

struct iscsi_session *session = cls_session->dd_data;

- struct module *owner = cls_session->transport->owner;
struct Scsi_Host *shost = session->host;

iscsi_remove_session(cls_session);
+ iscsi_host_dec_session_cnt(shost);
+}
+EXPORT_SYMBOL_GPL(iscsi_session_remove);
+
+/**
+ * iscsi_session_free - Free iscsi session and it's resources
+ * @cls_session: iscsi session
+ */
+void iscsi_session_free(struct iscsi_cls_session *cls_session)
+{
+ struct iscsi_session *session = cls_session->dd_data;
+ struct module *owner = cls_session->transport->owner;

iscsi_pool_free(&session->cmdpool);
kfree(session->password);
@@ -3132,10 +3142,19 @@ void iscsi_session_teardown(struct iscsi_cls_session *cls_session)
kfree(session->discovery_parent_type);

iscsi_free_session(cls_session);
-
- iscsi_host_dec_session_cnt(shost);
module_put(owner);
}
+EXPORT_SYMBOL_GPL(iscsi_session_free);
+
+/**
+ * iscsi_session_teardown - destroy session and cls_session
+ * @cls_session: iscsi session
+ */
+void iscsi_session_teardown(struct iscsi_cls_session *cls_session)
+{
+ iscsi_session_remove(cls_session);
+ iscsi_session_free(cls_session);
+}
EXPORT_SYMBOL_GPL(iscsi_session_teardown);

/**
diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h
index 695eebc6f2c8..5cdeff776ce2 100644
--- a/include/scsi/libiscsi.h
+++ b/include/scsi/libiscsi.h
@@ -422,6 +422,8 @@ extern int iscsi_host_get_max_scsi_cmds(struct Scsi_Host *shost,
extern struct iscsi_cls_session *
iscsi_session_setup(struct iscsi_transport *, struct Scsi_Host *shost,
uint16_t, int, int, uint32_t, unsigned int);
+extern void iscsi_session_remove(struct iscsi_cls_session *cls_session);
+extern void iscsi_session_free(struct iscsi_cls_session *cls_session);
extern void iscsi_session_teardown(struct iscsi_cls_session *);
extern void iscsi_session_recovery_timedout(struct iscsi_cls_session *);
extern int iscsi_set_param(struct iscsi_cls_conn *cls_conn,

[dinghui]

I applied your patch, and it works well.


Since this is more reasonable, could you ignore mine and submit your
patch instead please? I appreciate it.


--
Thanks,
-dinghui

[Wenchao Hao]

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/20210407012450.9...@huawei.com/

Because of my negligence, this bug has been discovered so far, and I
apologize for this.

[Mike Christie]

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.

[Ding Hui]

Hi Wenchao and Mike,

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

--
Thanks,
- Ding Hui