target: Avoid mappedlun symlink creation during lun shutdown
commit 49cb77e297
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@datera.io>
Cc: James Shen <jcs@datera.io>
Tested-by: James Shen <jcs@datera.io>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
08383b0044
commit
92f8aa7bb8
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@ -92,6 +92,11 @@ static int target_fabric_mappedlun_link(
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pr_err("Source se_lun->lun_se_dev does not exist\n");
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return -EINVAL;
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}
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if (lun->lun_shutdown) {
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pr_err("Unable to create mappedlun symlink because"
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" lun->lun_shutdown=true\n");
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return -EINVAL;
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}
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se_tpg = lun->lun_tpg;
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nacl_ci = &lun_acl_ci->ci_parent->ci_group->cg_item;
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@ -640,6 +640,8 @@ void core_tpg_remove_lun(
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*/
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struct se_device *dev = rcu_dereference_raw(lun->lun_se_dev);
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lun->lun_shutdown = true;
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core_clear_lun_from_tpg(lun, tpg);
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/*
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* Wait for any active I/O references to percpu se_lun->lun_ref to
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@ -661,6 +663,8 @@ void core_tpg_remove_lun(
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}
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if (!(dev->se_hba->hba_flags & HBA_FLAGS_INTERNAL_USE))
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hlist_del_rcu(&lun->link);
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lun->lun_shutdown = false;
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mutex_unlock(&tpg->tpg_lun_mutex);
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percpu_ref_exit(&lun->lun_ref);
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@ -705,6 +705,7 @@ struct se_lun {
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u64 unpacked_lun;
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#define SE_LUN_LINK_MAGIC 0xffff7771
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u32 lun_link_magic;
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bool lun_shutdown;
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bool lun_access_ro;
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u32 lun_index;
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