[ 3.5.y.z extended stable ] Patch "target: Fix divide by zero bug in fabric_max_sectors for" has been added to staging queue

Herton Ronaldo Krzesinski herton.krzesinski at canonical.com
Tue Feb 12 21:18:48 UTC 2013

This is a note to let you know that I have just added a patch titled

    target: Fix divide by zero bug in fabric_max_sectors for

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:


If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see



>From 72f89cb415897ee26509484e50db309b6887872b Mon Sep 17 00:00:00 2001
From: Nicholas Bellinger <nab at linux-iscsi.org>
Date: Thu, 31 Jan 2013 15:05:48 -0800
Subject: [PATCH] target: Fix divide by zero bug in fabric_max_sectors for
 unconfigured devices

commit 7a3cf6ca1ab2a2f7161c6dec5a787fc7a5de864e upstream.

This patch fixes a possible divide by zero bug when the fabric_max_sectors
device attribute is written and backend se_device failed to be successfully
configured -> enabled.

Go ahead and use block_size=512 within se_dev_set_fabric_max_sectors()
in the event of a target_configure_device() failure case, as no valid
dev->dev_attrib.block_size value will have been setup yet.

Signed-off-by: Nicholas Bellinger <nab at linux-iscsi.org>
[ herton: adjust context, block size is dev->se_sub_dev->se_dev_attrib.block_size ]
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
 drivers/target/target_core_device.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 8542099..0208baa 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -1167,6 +1167,8 @@ int se_dev_set_queue_depth(struct se_device *dev, u32 queue_depth)

 int se_dev_set_fabric_max_sectors(struct se_device *dev, u32 fabric_max_sectors)
+	int block_size = dev->se_sub_dev->se_dev_attrib.block_size;
 	if (atomic_read(&dev->dev_export_obj.obj_access_count)) {
 		pr_err("dev[%p]: Unable to change SE Device"
 			" fabric_max_sectors while dev_export_obj: %d count exists\n",
@@ -1204,8 +1206,12 @@ int se_dev_set_fabric_max_sectors(struct se_device *dev, u32 fabric_max_sectors)
 	 * Align max_sectors down to PAGE_SIZE to follow transport_allocate_data_tasks()
+	if (!block_size) {
+		block_size = 512;
+		pr_warn("Defaulting to 512 for zero block_size\n");
+	}
 	fabric_max_sectors = se_dev_align_max_sectors(fabric_max_sectors,
-						      dev->se_sub_dev->se_dev_attrib.block_size);
+						      block_size);

 	dev->se_sub_dev->se_dev_attrib.fabric_max_sectors = fabric_max_sectors;
 	pr_debug("dev[%p]: SE Device max_sectors changed to %u\n",

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