* [Linux-kernel-mentees] [PATCH] block: Fix use-after-free in bdev_del_partition()
[not found] <000000000000520ffc05ae2f4fee@google.com>
@ 2020-09-03 6:55 ` Peilin Ye
2020-09-03 6:59 ` Christoph Hellwig
0 siblings, 1 reply; 3+ messages in thread
From: Peilin Ye @ 2020-09-03 6:55 UTC (permalink / raw)
To: Jens Axboe
Cc: Hillf Danton, Jan Kara, Johannes Thumshirn, syzkaller-bugs,
linux-kernel, Ming Lei, linux-block, Christoph Hellwig,
Peilin Ye, Konstantin Khlebnikov, linux-kernel-mentees
In bdev_del_partition(), `part` is being looked up outside the critical
section. This is causing bdev_del_partition() to delete the same partition
more than once. Fix it by reverting commit cddae808aeb7.
Fixes: cddae808aeb7 ("block: pass a hd_struct to delete_partition")
Reported-and-tested-by: syzbot+6448f3c229bc52b82f69@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Cc: Hillf Danton <hdanton@sina.com>
Link: https://syzkaller.appspot.com/bug?id=09fc5ec437ea150f28e8a19f5011c08ee73381af
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
---
block/blk.h | 2 +-
block/genhd.c | 2 +-
block/partitions/core.c | 22 ++++++++++++++--------
3 files changed, 16 insertions(+), 10 deletions(-)
diff --git a/block/blk.h b/block/blk.h
index 49e2928a1632..f5a46d0020fb 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -350,7 +350,7 @@ char *disk_name(struct gendisk *hd, int partno, char *buf);
#define ADDPART_FLAG_NONE 0
#define ADDPART_FLAG_RAID 1
#define ADDPART_FLAG_WHOLEDISK 2
-void delete_partition(struct gendisk *disk, struct hd_struct *part);
+void delete_partition(struct gendisk *disk, int partno);
int bdev_add_partition(struct block_device *bdev, int partno,
sector_t start, sector_t length);
int bdev_del_partition(struct block_device *bdev, int partno);
diff --git a/block/genhd.c b/block/genhd.c
index 99c64641c314..40abc70b92ab 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -913,7 +913,7 @@ void del_gendisk(struct gendisk *disk)
DISK_PITER_INCL_EMPTY | DISK_PITER_REVERSE);
while ((part = disk_part_iter_next(&piter))) {
invalidate_partition(disk, part->partno);
- delete_partition(disk, part);
+ delete_partition(disk, part->partno);
}
disk_part_iter_exit(&piter);
diff --git a/block/partitions/core.c b/block/partitions/core.c
index e62a98a8eeb7..1fe1fe593423 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -310,17 +310,25 @@ int hd_ref_init(struct hd_struct *part)
* Must be called either with bd_mutex held, before a disk can be opened or
* after all disk users are gone.
*/
-void delete_partition(struct gendisk *disk, struct hd_struct *part)
+void delete_partition(struct gendisk *disk, int partno)
{
struct disk_part_tbl *ptbl =
rcu_dereference_protected(disk->part_tbl, 1);
+ struct hd_struct *part;
+
+ if (partno >= ptbl->len)
+ return;
+
+ part = rcu_dereference_protected(ptbl->part[partno], 1);
+ if (!part)
+ return;
/*
* ->part_tbl is referenced in this part's release handler, so
* we have to hold the disk device
*/
get_device(disk_to_dev(part_to_disk(part)));
- rcu_assign_pointer(ptbl->part[part->partno], NULL);
+ rcu_assign_pointer(ptbl->part[partno], NULL);
kobject_put(part->holder_dir);
device_del(part_to_dev(part));
@@ -531,10 +539,10 @@ int bdev_del_partition(struct block_device *bdev, int partno)
if (!part)
return -ENXIO;
- ret = -ENOMEM;
bdevp = bdget(part_devt(part));
+ disk_put_part(part);
if (!bdevp)
- goto out_put_part;
+ return -ENOMEM;
mutex_lock(&bdevp->bd_mutex);
@@ -546,15 +554,13 @@ int bdev_del_partition(struct block_device *bdev, int partno)
invalidate_bdev(bdevp);
mutex_lock_nested(&bdev->bd_mutex, 1);
- delete_partition(bdev->bd_disk, part);
+ delete_partition(bdev->bd_disk, partno);
mutex_unlock(&bdev->bd_mutex);
ret = 0;
out_unlock:
mutex_unlock(&bdevp->bd_mutex);
bdput(bdevp);
-out_put_part:
- disk_put_part(part);
return ret;
}
@@ -627,7 +633,7 @@ int blk_drop_partitions(struct block_device *bdev)
disk_part_iter_init(&piter, bdev->bd_disk, DISK_PITER_INCL_EMPTY);
while ((part = disk_part_iter_next(&piter)))
- delete_partition(bdev->bd_disk, part);
+ delete_partition(bdev->bd_disk, part->partno);
disk_part_iter_exit(&piter);
return 0;
--
2.25.1
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