[3.13.y-ckt stable] Patch "genhd: check for int overflow in disk_expand_part_tbl()" has been added to staging queue

[Kamal Mostafa]

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

    genhd: check for int overflow in disk_expand_part_tbl()

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt15.

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

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From deee66d98cc60d2a89934ce2b87d7c78c2e31906 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe at fb.com>
Date: Wed, 19 Nov 2014 13:06:22 -0700
Subject: genhd: check for int overflow in disk_expand_part_tbl()

commit 5fabcb4c33fe11c7e3afdf805fde26c1a54d0953 upstream.

We can get here from blkdev_ioctl() -> blkpg_ioctl() -> add_partition()
with a user passed in partno value. If we pass in 0x7fffffff, the
new target in disk_expand_part_tbl() overflows the 'int' and we
access beyond the end of ptbl->part[] and even write to it when we
do the rcu_assign_pointer() to assign the new partition.

Reported-by: David Ramos <daramos at stanford.edu>
Signed-off-by: Jens Axboe <axboe at fb.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 block/genhd.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index e6723bd..a8d586a 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1070,9 +1070,16 @@ int disk_expand_part_tbl(struct gendisk *disk, int partno)
 	struct disk_part_tbl *old_ptbl = disk->part_tbl;
 	struct disk_part_tbl *new_ptbl;
 	int len = old_ptbl ? old_ptbl->len : 0;
-	int target = partno + 1;
+	int i, target;
 	size_t size;
-	int i;
+
+	/*
+	 * check for int overflow, since we can get here from blkpg_ioctl()
+	 * with a user passed 'partno'.
+	 */
+	target = partno + 1;
+	if (target < 0)
+		return -EINVAL;

 	/* disk_max_parts() is zero during initialization, ignore if so */
 	if (disk_max_parts(disk) && target > disk_max_parts(disk))
--
1.9.1