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Date: Wed, 1 Nov 2017 22:25:41 +0100 From: Willy Tarreau <w@....eu> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org, linux@...ck-us.net Cc: Nicholas Bellinger <nab@...ux-iscsi.org>, James Shen <jcs@...era.io>, Willy Tarreau <w@....eu> Subject: [PATCH 3.10 044/139] target: Avoid mappedlun symlink creation during lun shutdown From: Nicholas Bellinger <nab@...ux-iscsi.org> commit 49cb77e297dc611a1b795cfeb79452b3002bd331 upstream. 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@...era.io> Cc: James Shen <jcs@...era.io> Tested-by: James Shen <jcs@...era.io> Cc: stable@...r.kernel.org Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org> Signed-off-by: Willy Tarreau <w@....eu> --- drivers/target/target_core_fabric_configfs.c | 5 +++++ drivers/target/target_core_tpg.c | 3 +++ include/target/target_core_base.h | 1 + 3 files changed, 9 insertions(+) diff --git a/drivers/target/target_core_fabric_configfs.c b/drivers/target/target_core_fabric_configfs.c index 04c775c..179f781 100644 --- a/drivers/target/target_core_fabric_configfs.c +++ b/drivers/target/target_core_fabric_configfs.c @@ -84,6 +84,11 @@ static int target_fabric_mappedlun_link( "_tpg 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_sep->sep_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 8572207..bc3092f 100644 --- a/drivers/target/target_core_tpg.c +++ b/drivers/target/target_core_tpg.c @@ -839,6 +839,8 @@ static void core_tpg_shutdown_lun( struct se_portal_group *tpg, struct se_lun *lun) { + lun->lun_shutdown = true; + core_clear_lun_from_tpg(lun, tpg); transport_clear_lun_from_sessions(lun); } @@ -868,6 +870,7 @@ struct se_lun *core_tpg_pre_dellun( spin_unlock(&tpg->tpg_lun_lock); return ERR_PTR(-ENODEV); } + lun->lun_shutdown = false; spin_unlock(&tpg->tpg_lun_lock); return lun; diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h index 7d99c0b..8e27143 100644 --- a/include/target/target_core_base.h +++ b/include/target/target_core_base.h @@ -729,6 +729,7 @@ struct se_port_stat_grps { struct se_lun { #define SE_LUN_LINK_MAGIC 0xffff7771 u32 lun_link_magic; + bool lun_shutdown; /* See transport_lun_status_table */ enum transport_lun_status_table lun_status; u32 lun_access; -- 2.8.0.rc2.1.gbe9624a
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