ext4: add more paranoia checking in ext4_expand_extra_isize handling
commit 4ea99936a1630f51fc3a2d61a58ec4a1c4b7d55a upstream.
It's possible to specify a non-zero s_want_extra_isize via debugging
option, and this can cause bad things(tm) to happen when using a file
system with an inode size of 128 bytes.
Add better checking when the file system is mounted, as well as when
we are actually doing the trying to do the inode expansion.
Link: https://lore.kernel.org/r/20191110121510.GH23325@mit.edu
Reported-by: syzbot+f8d6f8386ceacdbfff57@syzkaller.appspotmail.com
Reported-by: syzbot+33d7ea72e47de3bdf4e1@syzkaller.appspotmail.com
Reported-by: syzbot+44b6763edfc17144296f@syzkaller.appspotmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
[bwh: Backported to 4.9: adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index cea813a..391ab55 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3346,11 +3346,15 @@
{
struct ext4_sb_info *sbi = EXT4_SB(sb);
struct ext4_super_block *es = sbi->s_es;
+ unsigned def_extra_isize = sizeof(struct ext4_inode) -
+ EXT4_GOOD_OLD_INODE_SIZE;
- /* determine the minimum size of new large inodes, if present */
- if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE) {
- sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
- EXT4_GOOD_OLD_INODE_SIZE;
+ if (sbi->s_inode_size == EXT4_GOOD_OLD_INODE_SIZE) {
+ sbi->s_want_extra_isize = 0;
+ return;
+ }
+ if (sbi->s_want_extra_isize < 4) {
+ sbi->s_want_extra_isize = def_extra_isize;
if (ext4_has_feature_extra_isize(sb)) {
if (sbi->s_want_extra_isize <
le16_to_cpu(es->s_want_extra_isize))
@@ -3363,10 +3367,10 @@
}
}
/* Check if enough inode space is available */
- if (EXT4_GOOD_OLD_INODE_SIZE + sbi->s_want_extra_isize >
- sbi->s_inode_size) {
- sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
- EXT4_GOOD_OLD_INODE_SIZE;
+ if ((sbi->s_want_extra_isize > sbi->s_inode_size) ||
+ (EXT4_GOOD_OLD_INODE_SIZE + sbi->s_want_extra_isize >
+ sbi->s_inode_size)) {
+ sbi->s_want_extra_isize = def_extra_isize;
ext4_msg(sb, KERN_INFO,
"required extra inode space not available");
}