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authorNicholas Bellinger <nab@linux-iscsi.org>2017-03-27 16:12:43 -0700
committerNicholas Bellinger <nab@linux-iscsi.org>2017-03-30 01:36:52 -0700
commit49cb77e297dc611a1b795cfeb79452b3002bd331 (patch)
tree5a4b04abb770f691c69acf8a92277a6271137137
parentefb2ea770bb3b0f40007530bc8b0c22f36e1c5eb (diff)
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target: Avoid mappedlun symlink creation during lun shutdown
This patch closes a race between se_lun deletion during configfs unlink in target_fabric_port_unlink() -> core_dev_del_lun() -> core_tpg_remove_lun(), when transport_clear_lun_ref() blocks waiting for percpu_ref RCU grace period to finish, but a new NodeACL mappedlun is added before the RCU grace period has completed. This can happen in target_fabric_mappedlun_link() because it only checks for se_lun->lun_se_dev, which is not cleared until after transport_clear_lun_ref() percpu_ref RCU grace period finishes. This bug originally manifested as NULL pointer dereference OOPsen in target_stat_scsi_att_intr_port_show_attr_dev() on v4.1.y code, because it dereferences lun->lun_se_dev without a explicit NULL pointer check. In post v4.1 code with target-core RCU conversion, the code in target_stat_scsi_att_intr_port_show_attr_dev() no longer uses se_lun->lun_se_dev, but the same race still exists. To address the bug, go ahead and set se_lun>lun_shutdown as early as possible in core_tpg_remove_lun(), and ensure new NodeACL mappedlun creation in target_fabric_mappedlun_link() fails during se_lun shutdown. Reported-by: James Shen <jcs@datera.io> Cc: James Shen <jcs@datera.io> Tested-by: James Shen <jcs@datera.io> Cc: stable@vger.kernel.org # 3.10+ Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
-rw-r--r--drivers/target/target_core_fabric_configfs.c5
-rw-r--r--drivers/target/target_core_tpg.c4
-rw-r--r--include/target/target_core_base.h1
3 files changed, 10 insertions, 0 deletions
diff --git a/drivers/target/target_core_fabric_configfs.c b/drivers/target/target_core_fabric_configfs.c
index d8a16ca6baa5..d1e6cab8e3d3 100644
--- a/drivers/target/target_core_fabric_configfs.c
+++ b/drivers/target/target_core_fabric_configfs.c
@@ -92,6 +92,11 @@ static int target_fabric_mappedlun_link(
pr_err("Source se_lun->lun_se_dev does not exist\n");
return -EINVAL;
}
+ if (lun->lun_shutdown) {
+ pr_err("Unable to create mappedlun symlink because"
+ " lun->lun_shutdown=true\n");
+ return -EINVAL;
+ }
se_tpg = lun->lun_tpg;
nacl_ci = &lun_acl_ci->ci_parent->ci_group->cg_item;
diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c
index 6fb191914f45..dfaef4d3b2d2 100644
--- a/drivers/target/target_core_tpg.c
+++ b/drivers/target/target_core_tpg.c
@@ -642,6 +642,8 @@ void core_tpg_remove_lun(
*/
struct se_device *dev = rcu_dereference_raw(lun->lun_se_dev);
+ lun->lun_shutdown = true;
+
core_clear_lun_from_tpg(lun, tpg);
/*
* Wait for any active I/O references to percpu se_lun->lun_ref to
@@ -663,6 +665,8 @@ void core_tpg_remove_lun(
}
if (!(dev->se_hba->hba_flags & HBA_FLAGS_INTERNAL_USE))
hlist_del_rcu(&lun->link);
+
+ lun->lun_shutdown = false;
mutex_unlock(&tpg->tpg_lun_mutex);
percpu_ref_exit(&lun->lun_ref);
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 4b784b6e21c0..2e282461cfa5 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -705,6 +705,7 @@ struct se_lun {
u64 unpacked_lun;
#define SE_LUN_LINK_MAGIC 0xffff7771
u32 lun_link_magic;
+ bool lun_shutdown;
bool lun_access_ro;
u32 lun_index;