[ 3.5.y.z extended stable ] Patch "target: Avoid integer overflow in se_dev_align_max_sectors()" has been added to staging queue

[Herton Ronaldo Krzesinski]

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

    target: Avoid integer overflow in se_dev_align_max_sectors()

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

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

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
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From 1f66d2d5d4094baeafa28a1b729ab7c5a1e63030 Mon Sep 17 00:00:00 2001
From: Roland Dreier <roland at purestorage.com>
Date: Wed, 31 Oct 2012 09:16:45 -0700
Subject: [PATCH] target: Avoid integer overflow in se_dev_align_max_sectors()
X-Extended-Stable: 3.5

commit 3e03989b5868acf69a391a424dc71fcd6cc48167 upstream.

The expression (max_sectors * block_size) might overflow a u32
(indeed, since iblock sets max_hw_sectors to UINT_MAX, it is
guaranteed to overflow and end up with a much-too-small result in many
common cases).  Fix this by doing an equivalent calculation that
doesn't require multiplication.

While we're touching this code, avoid splitting a printk format across
two lines and use pr_info(...) instead of printk(KERN_INFO ...).

Signed-off-by: Roland Dreier <roland at purestorage.com>
Signed-off-by: Nicholas Bellinger <nab at linux-iscsi.org>
[ herton: unfuzz patch ]
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 drivers/target/target_core_device.c |   18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 5ad9728..8542099 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -824,20 +824,20 @@ int se_dev_check_shutdown(struct se_device *dev)

 u32 se_dev_align_max_sectors(u32 max_sectors, u32 block_size)
 {
-	u32 tmp, aligned_max_sectors;
+	u32 aligned_max_sectors;
+	u32 alignment;
 	/*
 	 * Limit max_sectors to a PAGE_SIZE aligned value for modern
 	 * transport_allocate_data_tasks() operation.
 	 */
-	tmp = rounddown((max_sectors * block_size), PAGE_SIZE);
-	aligned_max_sectors = (tmp / block_size);
-	if (max_sectors != aligned_max_sectors) {
-		printk(KERN_INFO "Rounding down aligned max_sectors from %u"
-				" to %u\n", max_sectors, aligned_max_sectors);
-		return aligned_max_sectors;
-	}
+	alignment = max(1ul, PAGE_SIZE / block_size);
+	aligned_max_sectors = rounddown(max_sectors, alignment);
+
+	if (max_sectors != aligned_max_sectors)
+		pr_info("Rounding down aligned max_sectors from %u to %u\n",
+			max_sectors, aligned_max_sectors);

-	return max_sectors;
+	return aligned_max_sectors;
 }

 void se_dev_set_default_attribs(
--
1.7.9.5