diff options
| author | Theodore Ts'o <tytso@mit.edu> | 2016-07-05 20:01:52 -0400 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2016-11-20 01:01:24 +0000 |
| commit | 03eaa7470b473b98aacb14dee2d9e9d296307c78 (patch) | |
| tree | 321a04fbbffa2a0f41c05383cd9aa823fbf2866b /fs | |
| parent | 90a737fbbbfb5842874ba203e54fd5406b532a90 (diff) | |
ext4: validate s_reserved_gdt_blocks on mount
commit 5b9554dc5bf008ae7f68a52e3d7e76c0920938a2 upstream.
If s_reserved_gdt_blocks is extremely large, it's possible for
ext4_init_block_bitmap(), which is called when ext4 sets up an
uninitialized block bitmap, to corrupt random kernel memory. Add the
same checks which e2fsck has --- it must never be larger than
blocksize / sizeof(__u32) --- and then add a backup check in
ext4_init_block_bitmap() in case the superblock gets modified after
the file system is mounted.
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
[bwh: Backported to 3.2:
- Drop the second check in ext4_init_block_bitmap() since it can't return
an error code
- Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/ext4/super.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 52b8ac740201..0d3204948ada 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3429,6 +3429,13 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) goto failed_mount; } + if (le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks) > (blocksize / 4)) { + ext4_msg(sb, KERN_ERR, + "Number of reserved GDT blocks insanely large: %d", + le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks)); + goto failed_mount; + } + if (sb->s_blocksize != blocksize) { /* Validate the filesystem blocksize */ if (!sb_set_blocksize(sb, blocksize)) { |