linux-kernel - [PATCH 3.13.y-ckt 037/139] genhd: check for int overflow in disk_expand_part

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Message-Id: <1422483682-15393-38-git-send-email-kamal@canonical.com>
Date:	Wed, 28 Jan 2015 14:19:40 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Jens Axboe <axboe@...com>, Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13.y-ckt 037/139] genhd: check for int overflow in disk_expand_part_tbl()

3.13.11-ckt15 -stable review patch.  If anyone has any objections, please let me know.

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

From: Jens Axboe <axboe@...com>

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@...nford.edu>
Signed-off-by: Jens Axboe <axboe@...com>
Signed-off-by: Kamal Mostafa <kamal@...onical.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

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