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Hello，
Anyone looking this？
在 2023/2/13 11:43, Zhong Jinghua 写道:
From: Zhong Jinghua <zhongjinghua@xxxxxxxxxx>
A use-after-free problem like below:
BUG: KASAN: use-after-free in scsi_target_reap+0x6c/0x70
Workqueue: scsi_wq_1 __iscsi_unbind_session [scsi_transport_iscsi]
Call trace:
dump_backtrace+0x0/0x320
show_stack+0x24/0x30
dump_stack+0xdc/0x128
print_address_description+0x68/0x278
kasan_report+0x1e4/0x308
__asan_report_load4_noabort+0x30/0x40
scsi_target_reap+0x6c/0x70
scsi_remove_target+0x430/0x640
__iscsi_unbind_session+0x164/0x268 [scsi_transport_iscsi]
process_one_work+0x67c/0x1350
worker_thread+0x370/0xf90
kthread+0x2a4/0x320
ret_from_fork+0x10/0x18
The problem is caused by a concurrency scenario:
T0: delete target
// echo 1 > /sys/devices/platform/host1/session1/target1:0:0/1:0:0:1/delete
T1: logout
// iscsiadm -m node --logout
T0 T1
sdev_store_delete
scsi_remove_device
device_remove_file
__scsi_remove_device
__iscsi_unbind_session
scsi_remove_target
spin_lock_irqsave
list_for_each_entry
scsi_target_reap // starget->reaf 1 -> 0
kref_get(&starget->reap_ref);
// warn use-after-free.
spin_unlock_irqrestore
scsi_target_reap_ref_release
scsi_target_destroy
... // delete starget
scsi_target_reap
// UAF
When T0 reduces the reference count to 0, but has not been released,
T1 can still enter list_for_each_entry, and then kref_get reports UAF.
Fix it by using kref_get_unless_zero() to check for a reference count of
0.
Signed-off-by: Zhong Jinghua <zhongjinghua@xxxxxxxxxx>
---
drivers/scsi/scsi_sysfs.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index e7893835b99a..0ad357ff4c59 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1561,7 +1561,17 @@ void scsi_remove_target(struct device *dev)
starget->state == STARGET_CREATED_REMOVE)
continue;
if (starget->dev.parent == dev || &starget->dev == dev) {
- kref_get(&starget->reap_ref);
+
+ /*
+ * If starget->reap_ref is reduced to 0, it means
+ * that other processes are releasing it and
+ * there is no need to delete it again
+ */
+ if (!kref_get_unless_zero(&starget->reap_ref)) {
+ spin_unlock_irqrestore(shost->host_lock, flags);
+ goto restart;
+ }
+
if (starget->state == STARGET_CREATED)
starget->state = STARGET_CREATED_REMOVE;
else
