[PATCH v2 0/2] scsi: iscsi: host ipaddress UAF fixes

[PATCH v2 0/2] scsi: iscsi: host ipaddress UAF fixes

[Mike Christie]

The following patches made apply over Martin's or Linus's trees. They
fix 2 use after free bugs caused by iscsi_tcp using the session's socket
to export the local IP address on the iscsi host to emulate the host's
local IP address.

Note that the naming is not great because the libiscsi session removal
and freeing functions are close to the iSCSI class's names. That will be
fixed in a separate patch for the 6.3 or 6.4 kernel (depending on when
this is merged) because it was a pretty big change fix up all the naming.

v2:
- Fix bug reproducer example in git commit message.

[PATCH v2 1/2] scsi: iscsi_tcp: Fix UAF during logout when accessing the shost ipaddress

[Mike Christie]

Bug report and analysis from Ding Hui.

During iscsi session logout, if another task accesses the shost ipaddress
attr, we can get a KASAN UAF report like this:

[  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            |

This patch fixes the above bug by splitting the session removal into 2
parts:
1. removal from iSCSI class which includes sysfs and removal from host
tracking.
2. freeing of session.

During iscsi_tcp host and session removal we can remove the session from
sysfs then remove the host from sysfs. At this point we know userspace is
not accessing the kernel via sysfs so we can free the session and host.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
---
 drivers/scsi/iscsi_tcp.c | 11 +++++++++--
 drivers/scsi/libiscsi.c  | 38 +++++++++++++++++++++++++++++++-------
 include/scsi/libiscsi.h  |  2 ++
 3 files changed, 42 insertions(+), 9 deletions(-)

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 5fb1f364e815..9c0c8f34ef67 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -982,10 +982,17 @@ 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);
+	/*
+	 * Our get_host_param needs to access the session, so remove the
+	 * host from sysfs before freeing the session to make sure userspace
+	 * is no longer accessing the callout.
+	 */
+	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 d95f4bcdeb2e..6e811d753cb1 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -3104,17 +3104,32 @@ 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);
+	/*
+	 * host removal only has to wait for its children to be removed from
+	 * sysfs, and iscsi_tcp needs to do iscsi_host_remove before freeing
+	 * the session, so drop the session count here.
+	 */
+	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 +3147,19 @@ 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 654cc3918c94..7523b6abd8e2 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);
+void iscsi_session_remove(struct iscsi_cls_session *cls_session);
+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,
-- 
2.25.1

[PATCH v2 2/2] scsi: iscsi_tcp: Fix UAF during login when accessing the shost ipaddress

[Mike Christie]

If during iscsi_sw_tcp_session_create iscsi_tcp_r2tpool_alloc fails
userspace could be accessing the host's ipaddress attr. If we then
free the session via iscsi_session_teardown while userspace is still
accessing the session we will hit a use after free bug.

This patch has us set the tcp_sw_host->session after we have completed
session creation and can no longer fail.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
---
 drivers/scsi/iscsi_tcp.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 9c0c8f34ef67..c3ad04ad66e0 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -848,7 +848,7 @@ static int iscsi_sw_tcp_host_get_param(struct Scsi_Host *shost,
 				       enum iscsi_host_param param, char *buf)
 {
 	struct iscsi_sw_tcp_host *tcp_sw_host = iscsi_host_priv(shost);
-	struct iscsi_session *session = tcp_sw_host->session;
+	struct iscsi_session *session;
 	struct iscsi_conn *conn;
 	struct iscsi_tcp_conn *tcp_conn;
 	struct iscsi_sw_tcp_conn *tcp_sw_conn;
@@ -858,6 +858,7 @@ static int iscsi_sw_tcp_host_get_param(struct Scsi_Host *shost,
 
 	switch (param) {
 	case ISCSI_HOST_PARAM_IPADDRESS:
+		session = tcp_sw_host->session;
 		if (!session)
 			return -ENOTCONN;
 
@@ -958,11 +959,13 @@ iscsi_sw_tcp_session_create(struct iscsi_endpoint *ep, uint16_t cmds_max,
 	if (!cls_session)
 		goto remove_host;
 	session = cls_session->dd_data;
-	tcp_sw_host = iscsi_host_priv(shost);
-	tcp_sw_host->session = session;
 
 	if (iscsi_tcp_r2tpool_alloc(session))
 		goto remove_session;
+
+	/* We are now fully setup so expose the session to sysfs. */
+	tcp_sw_host = iscsi_host_priv(shost);
+	tcp_sw_host->session = session;
 	return cls_session;
 
 remove_session:
-- 
2.25.1

Re: [PATCH v2 0/2] scsi: iscsi: host ipaddress UAF fixes

[Ding Hui]

On 2023/1/18 3:39, Mike Christie wrote:
> The following patches made apply over Martin's or Linus's trees. They
> fix 2 use after free bugs caused by iscsi_tcp using the session's socket
> to export the local IP address on the iscsi host to emulate the host's
> local IP address.
> 
> Note that the naming is not great because the libiscsi session removal
> and freeing functions are close to the iSCSI class's names. That will be
> fixed in a separate patch for the 6.3 or 6.4 kernel (depending on when
> this is merged) because it was a pretty big change fix up all the naming.
> 
> v2:
> - Fix bug reproducer example in git commit message.
> 

It looks good to me.

Thanks for your work on this.

-- 
Thanks,
- Ding Hui

Re: [PATCH v2 0/2] scsi: iscsi: host ipaddress UAF fixes

[Lee Duncan]

On 1/17/23 11:39, Mike Christie wrote:
> The following patches made apply over Martin's or Linus's trees. They
> fix 2 use after free bugs caused by iscsi_tcp using the session's socket
> to export the local IP address on the iscsi host to emulate the host's
> local IP address.
> 
> Note that the naming is not great because the libiscsi session removal
> and freeing functions are close to the iSCSI class's names. That will be
> fixed in a separate patch for the 6.3 or 6.4 kernel (depending on when
> this is merged) because it was a pretty big change fix up all the naming.
> 
> v2:
> - Fix bug reproducer example in git commit message.
> 
> 
> 

Both patches look good to me.

Reviewed-by: Lee Duncan <lduncan@suse.com>

Re: [PATCH v2 0/2] scsi: iscsi: host ipaddress UAF fixes

[Martin K. Petersen]

Mike,

> The following patches made apply over Martin's or Linus's trees. They
> fix 2 use after free bugs caused by iscsi_tcp using the session's socket
> to export the local IP address on the iscsi host to emulate the host's
> local IP address.
>
> Note that the naming is not great because the libiscsi session removal
> and freeing functions are close to the iSCSI class's names. That will be
> fixed in a separate patch for the 6.3 or 6.4 kernel (depending on when
> this is merged) because it was a pretty big change fix up all the naming.

Applied to 6.2/scsi-fixes, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering