[PATCH 5.10 099/103] block: fix use-after-free in disk_part_iter_next
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2021-01-15 12:41:25
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From: Ming Lei <redacted> commit aebf5db917055b38f4945ed6d621d9f07a44ff30 upstream. Make sure that bdgrab() is done on the 'block_device' instance before referring to it for avoiding use-after-free. Cc: <redacted> Reported-by: syzbot+825f0f9657d4e528046e@syzkaller.appspotmail.com Signed-off-by: Ming Lei <redacted> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- block/genhd.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
--- a/block/genhd.c
+++ b/block/genhd.c@@ -256,14 +256,17 @@ struct hd_struct *disk_part_iter_next(st part = rcu_dereference(ptbl->part[piter->idx]); if (!part) continue; + get_device(part_to_dev(part)); + piter->part = part; if (!part_nr_sects_read(part) && !(piter->flags & DISK_PITER_INCL_EMPTY) && !(piter->flags & DISK_PITER_INCL_EMPTY_PART0 && - piter->idx == 0)) + piter->idx == 0)) { + put_device(part_to_dev(part)); + piter->part = NULL; continue; + } - get_device(part_to_dev(part)); - piter->part = part; piter->idx += inc; break; }