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@linux-iscsi.org>
Cc: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 0943ff06d82e6379a532faf4581a9b26cec6d5e9..94fda907b8e6a58d54533588e4c751ed9f8e354f 100644 (file)
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -1195,6 +1195,8 @@ 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",
@@ -1232,8 +1234,12 @@ 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",