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[PATCH 4.9 25/60] target: Dont BUG_ON during NodeACL dynamic -> explicit conversion

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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Bellinger <nab@linux-iscsi.org>

commit 391e2a6de9781e4906dd7e0b1cc097050bf43e11 upstream.

After the v4.2+ RCU conversion to se_node_acl->lun_entry_hlist,
a BUG_ON() was added in core_enable_device_list_for_node() to
detect when the located orig->se_lun_acl contains an existing
se_lun_acl pointer reference.

However, this scenario can happen when a dynamically generated
NodeACL is being converted to an explicit NodeACL, when the
explicit NodeACL contains a different LUN mapping than the
default provided by the WWN endpoint.

So instead of triggering BUG_ON(), go ahead and fail instead
following the original pre RCU conversion logic.

Reported-by: Benjamin ESTRABAUD <ben.estrabaud@mpstor.com>
Cc: Benjamin ESTRABAUD <ben.estrabaud@mpstor.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/target/target_core_device.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -351,7 +351,15 @@ int core_enable_device_list_for_node(
 			kfree(new);
 			return -EINVAL;
 		}
-		BUG_ON(orig->se_lun_acl != NULL);
+		if (orig->se_lun_acl != NULL) {
+			pr_warn_ratelimited("Detected existing explicit"
+				" se_lun_acl->se_lun_group reference for %s"
+				" mapped_lun: %llu, failing\n",
+				 nacl->initiatorname, mapped_lun);
+			mutex_unlock(&nacl->lun_entry_mutex);
+			kfree(new);
+			return -EINVAL;
+		}
 
 		rcu_assign_pointer(new->se_lun, lun);
 		rcu_assign_pointer(new->se_lun_acl, lun_acl);

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[PATCH 4.9 00/60] 4.9.10-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 11/60] crypto: ccp - Fix double add when creating new DMA command Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 09/60] crypto: qat - zero esram only for DH85x devices Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 20/60] hns: avoid stack overflow with CONFIG_KASAN Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 05/60] dm rq: cope with DM device destruction while in dm_old_request_fn() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 21/60] ARM: 8643/3: arm/ptrace: Preserve previous registers for short regset write Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 12/60] ARC: [arcompact] brown paper bag bug in unaligned access delay slot fixup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 18/60] mm/slub.c: fix random_seq offset destruction Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 28/60] target: Fix multi-session dynamic se_node_acl double free OOPs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 03/60] libnvdimm, namespace: do not delete namespace-id 0 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 24/60] drm/atomic: Fix double free in drm_atomic_state_default_clear Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 07/60] crypto: chcr - Check device is allocated before use Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 26/60] target: Use correct SCSI status during EXTENDED_COPY exception Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 02/60] acpi, nfit: fix acpi_nfit_flush_probe() crash Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 13/60] Input: uinput - fix crash when mixing old and new init style Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 19/60] ibmvscsis: Add SGL limit Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  [PATCH 4.9 25/60] target: Dont BUG_ON during NodeACL dynamic -> explicit conversion Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 14:30 +0100
  Re: [PATCH 4.9 00/60] 4.9.10-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-02-13 18:10 +0100
    Re: [PATCH 4.9 00/60] 4.9.10-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-13 18:30 +0100
  Re: [PATCH 4.9 00/60] 4.9.10-stable review Guenter Roeck <linux@roeck-us.net> - 2017-02-13 21:10 +0100
    Re: [PATCH 4.9 00/60] 4.9.10-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-15 00:00 +0100

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