linux-ext4 - [PATCH 3/5] libext2fs: add stricter checks on the inode size in ext2fs

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Date:   Sun, 23 Jul 2017 00:50:33 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc:     abuchbinder@...gle.com, Theodore Ts'o <tytso@....edu>
Subject: [PATCH 3/5] libext2fs: add stricter checks on the inode size in ext2fs_open2()

An inode size larger than the block size can cause userspace programs
to crash.

This problem was found using American Fuzzy Lop.

Reported-by: Adam Buchbinder <abuchbinder@...gle.com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
---
 lib/ext2fs/openfs.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/ext2fs/openfs.c b/lib/ext2fs/openfs.c
index 0362b2839..da03bc147 100644
--- a/lib/ext2fs/openfs.c
+++ b/lib/ext2fs/openfs.c
@@ -121,6 +121,7 @@ errcode_t ext2fs_open2(const char *name, const char *io_options,
 	blk64_t		group_block, blk;
 	char		*dest, *cp;
 	int		group_zero_adjust = 0;
+	int		inode_size;
 #ifdef WORDS_BIGENDIAN
 	unsigned int	groups_per_block;
 	struct ext2_group_desc *gdp;
@@ -297,7 +298,10 @@ errcode_t ext2fs_open2(const char *name, const char *io_options,
 		goto cleanup;
 	}
 	fs->fragsize = fs->blocksize = EXT2_BLOCK_SIZE(fs->super);
-	if (EXT2_INODE_SIZE(fs->super) < EXT2_GOOD_OLD_INODE_SIZE) {
+	inode_size = EXT2_INODE_SIZE(fs->super);
+	if ((inode_size < EXT2_GOOD_OLD_INODE_SIZE) ||
+	    (inode_size > fs->blocksize) ||
+	    (inode_size & (inode_size - 1))) {
 		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 		goto cleanup;
 	}
-- 
2.11.0.rc0.7.gbe5a750