blob: 9a2d356a48ef8aa3a2020f2744a3206ddbc7b993 [file] [log] [blame]
From: Theodore Ts'o <tytso@mit.edu>
Date: Tue, 5 Jul 2016 20:01:52 -0400
Subject: 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>
---
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3429,6 +3429,13 @@ static int ext4_fill_super(struct super_
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)) {