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block: fix use-after-free in disk_part_iter_next 

Make sure that bdgrab() is done on the 'block_device' instance before
referring to it for avoiding use-after-free.

Cc: <stable@vger.kernel.org>
Reported-by: syzbot+825f0f9657d4e528046e@syzkaller.appspotmail.com
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2020-12-21 12:33:35 +08:00 committed by Jens Axboe
parent 6d4d273588
commit aebf5db917
1 changed files with 9 additions and 6 deletions
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15
block/genhd.c
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@ -246,15 +246,18 @@ struct block_device *disk_part_iter_next(struct disk_part_iter *piter)
part = rcu_dereference(ptbl->part[piter->idx]); part = rcu_dereference(ptbl->part[piter->idx]);
if (!part) if (!part)
continue; continue;
if (!bdev_nr_sectors(part) &&
!(piter->flags & DISK_PITER_INCL_EMPTY) &&
!(piter->flags & DISK_PITER_INCL_EMPTY_PART0 &&
piter->idx == 0))
continue;
piter->part = bdgrab(part); piter->part = bdgrab(part);
if (!piter->part) if (!piter->part)
continue; continue;
if (!bdev_nr_sectors(part) &&
!(piter->flags & DISK_PITER_INCL_EMPTY) &&
!(piter->flags & DISK_PITER_INCL_EMPTY_PART0 &&
piter->idx == 0)) {
bdput(piter->part);
piter->part = NULL;
continue;
}
piter->idx += inc; piter->idx += inc;
break; break;
} }