linux-ext4 - [PATCH 2/2] ext2fs: Fix off-by-one in dx_grow

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Date:   Mon, 30 Mar 2020 11:09:32 +0200
From:   Jan Kara <jack@...e.cz>
To:     Ted Tso <tytso@....edu>
Cc:     <linux-ext4@...r.kernel.org>, Jan Kara <jack@...e.cz>
Subject: [PATCH 2/2] ext2fs: Fix off-by-one in dx_grow_tree()

There is an off-by-one error in dx_grow_tree() when checking whether we
can add another level to the tree. Thus we can grow tree too much
leading to possible crashes in the library or corrupted filesystem. Fix
the bug.

Signed-off-by: Jan Kara <jack@...e.cz>
---
 lib/ext2fs/link.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/ext2fs/link.c b/lib/ext2fs/link.c
index 7b5bb022117c..469eea8cd06d 100644
--- a/lib/ext2fs/link.c
+++ b/lib/ext2fs/link.c
@@ -473,7 +473,7 @@ static errcode_t dx_grow_tree(ext2_filsys fs, ext2_ino_t dir,
 		    ext2fs_le16_to_cpu(info->frames[i].head->limit))
 			break;
 	/* Need to grow tree depth? */
-	if (i < 0 && info->levels > ext2_dir_htree_level(fs))
+	if (i < 0 && info->levels >= ext2_dir_htree_level(fs))
 		return EXT2_ET_DIR_NO_SPACE;
 	lblk = size / fs->blocksize;
 	size += fs->blocksize;
-- 
2.16.4