Commit 97b19170 authored Jul 13, 2018 by Naohiro Aota Committed by David Sterba Jul 13, 2018

btrfs: fix use-after-free of cmp workspace pages



btrfs_cmp_data_free() puts cmp's src_pages and dst_pages, but leaves
their page address intact. Now, if you hit "goto again" in
btrfs_extent_same_range() and hit some error in
btrfs_cmp_data_prepare(), you'll try to unlock/put already put pages.

This is simple fix to reset the address to avoid use-after-free.

Fixes: 67b07bd4 ("Btrfs: reuse cmp workspace in EXTENT_SAME ioctl")
Signed-off-by: Naohiro Aota <naota@elisp.net>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

parent 20c5bbc6

fs/btrfs/ioctl.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -3327,11 +3327,13 @@ static void btrfs_cmp_data_free(struct cmp_pages *cmp)
		if (pg) {
		unlock_page(pg);
		put_page(pg);
		cmp->src_pages[i] = NULL;
		}
		pg = cmp->dst_pages[i];
		if (pg) {
		unlock_page(pg);
		put_page(pg);
		cmp->dst_pages[i] = NULL;
		}
		}
		}

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