[PATCH 3.18 089/150] genhd: check for int overflow in disk_expand_part_tbl()

Greg Kroah-Hartman
2015-01-14T07:30:55Z

From: Jens Axboe <axboe@fb.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@stanford.edu>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
block/genhd.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1070,9 +1070,16 @@ int disk_expand_part_tbl(struct gendisk
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))