In part_release(), it will remove devt from ext_devt_idr and
get_gendisk cannot find it. But, if disk_release() works before
part_release, open device partition may cause use-after-free of
disk in get_gendisk(). We use md device as example, the race sence:
Process1 Worker Process2
md_free
blkdev_open
del_gendisk
add delete_partition_work_fn() to wq
__blkdev_get
get_gendisk
put_disk
disk_release
kfree(disk)
find part from ext_devt_idr
get_disk_and_module(disk)
cause use after free
delete_partition_work_fn
put_device(part)
part_release
remove part from ext_devt_idr
Before Woker thread removes part from ext_devt_idr, Process2 can find
the part and access the disk, resulting use-after-free.
We fix this by removing the devt from ext_devt_idr when delete partition.
Signed-off-by: Yufen Yu <yuyufen@xxxxxxxxxx>
---
block/partition-generic.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/block/partition-generic.c b/block/partition-generic.c
index 1ee3e1d1bc2a..30d1039d5e8d 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -288,6 +288,11 @@ void delete_partition(struct gendisk *disk, int partno)
kobject_put(part->holder_dir);
device_del(part_to_dev(part));
+ /*
+ * We should ensuere to delete part from idr before kfree(disk),
+ * avoiding use-after-free of disk.
+ */
+ blk_free_devt(part_devt(part));
hd_struct_kill(part);
}
--
2.16.2.dirty
