[PATCH AUTOSEL 5.4 095/134] scsi: target: core: Release SPC-2 reservations when closing a session

Sasha Levin
2019-12-11T15:13:37Z

From: Bart Van Assche <bvanassche@acm.org>

[ Upstream commit 80647a89eaf3f2549741648f3230cd6ff68c23b4 ]

The SCSI specs require releasing SPC-2 reservations when a session is
closed. Make sure that the target core does this.

Running the libiscsi tests triggers the KASAN complaint shown below. This
patch fixes that use-after-free.

BUG: KASAN: use-after-free in target_check_reservation+0x171/0x980 [target_core_mod]
Read of size 8 at addr ffff88802ecd1878 by task iscsi_trx/17200

CPU: 0 PID: 17200 Comm: iscsi_trx Not tainted 5.4.0-rc1-dbg+ #1
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Call Trace:
dump_stack+0x8a/0xd6
print_address_description.constprop.0+0x40/0x60
__kasan_report.cold+0x1b/0x34
kasan_report+0x16/0x20
__asan_load8+0x58/0x90
target_check_reservation+0x171/0x980 [target_core_mod]
__target_execute_cmd+0xb1/0xf0 [target_core_mod]
target_execute_cmd+0x22d/0x4d0 [target_core_mod]
transport_generic_new_cmd+0x31f/0x5b0 [target_core_mod]
transport_handle_cdb_direct+0x6f/0x90 [target_core_mod]
iscsit_execute_cmd+0x381/0x3f0 [iscsi_target_mod]
iscsit_sequence_cmd+0x13b/0x1f0 [iscsi_target_mod]
iscsit_process_scsi_cmd+0x4c/0x130 [iscsi_target_mod]
iscsit_get_rx_pdu+0x8e8/0x15f0 [iscsi_target_mod]
iscsi_target_rx_thread+0x105/0x1b0 [iscsi_target_mod]
kthread+0x1bc/0x210
ret_from_fork+0x24/0x30

Allocated by task 1079:
save_stack+0x23/0x90
__kasan_kmalloc.constprop.0+0xcf/0xe0
kasan_slab_alloc+0x12/0x20
kmem_cache_alloc+0xfe/0x3a0
transport_alloc_session+0x29/0x80 [target_core_mod]
iscsi_target_login_thread+0xceb/0x1920 [iscsi_target_mod]
kthread+0x1bc/0x210
ret_from_fork+0x24/0x30

Freed by task 17193:
save_stack+0x23/0x90
__kasan_slab_free+0x13a/0x190
kasan_slab_free+0x12/0x20
kmem_cache_free+0xc8/0x3e0
transport_free_session+0x179/0x2f0 [target_core_mod]
transport_deregister_session+0x121/0x170 [target_core_mod]
iscsit_close_session+0x12c/0x350 [iscsi_target_mod]
iscsit_logout_post_handler+0x136/0x380 [iscsi_target_mod]
iscsit_response_queue+0x8fa/0xc00 [iscsi_target_mod]
iscsi_target_tx_thread+0x28e/0x390 [iscsi_target_mod]
kthread+0x1bc/0x210
ret_from_fork+0x24/0x30

The buggy address belongs to the object at ffff88802ecd1860
which belongs to the cache se_sess_cache of size 352
The buggy address is located 24 bytes inside of
352-byte region [ffff88802ecd1860, ffff88802ecd19c0)
The buggy address belongs to the page:
page:ffffea0000bb3400 refcount:1 mapcount:0 mapping:ffff8880bef2ed00 index:0x0 compound_mapcount: 0
flags: 0x1000000000010200(slab|head)
raw: 1000000000010200 dead000000000100 dead000000000122 ffff8880bef2ed00
raw: 0000000000000000 0000000080270027 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88802ecd1700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88802ecd1780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802ecd1800: fb fb fb fb fc fc fc fc fc fc fc fc fb fb fb fb
^
ffff88802ecd1880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88802ecd1900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

Cc: Mike Christie <mchristi@redhat.com>
Link: https://lore.kernel.org/r/20191113220508.198257-2-bvanassche@acm.org
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/target/target_core_transport.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 7f06a62f8661d..eda8b4736c158 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -584,6 +584,15 @@ void transport_free_session(struct se_session *se_sess)
}
EXPORT_SYMBOL(transport_free_session);

+static int target_release_res(struct se_device *dev, void *data)
+{
+ struct se_session *sess = data;
+
+ if (dev->reservation_holder == sess)
+ target_release_reservation(dev);
+ return 0;
+}
+
void transport_deregister_session(struct se_session *se_sess)
{
struct se_portal_group *se_tpg = se_sess->se_tpg;
@@ -600,6 +609,12 @@ void transport_deregister_session(struct se_session *se_sess)
se_sess->fabric_sess_ptr = NULL;
spin_unlock_irqrestore(&se_tpg->session_lock, flags);

+ /*
+ * Since the session is being removed, release SPC-2
+ * reservations held by the session that is disappearing.
+ */
+ target_for_each_device(target_release_res, se_sess);
+
pr_debug("TARGET_CORE[%s]: Deregistered fabric_sess\n",
se_tpg->se_tpg_tfo->fabric_name);
/*
--
2.20.1