ext4: add more paranoia checking in ext4_expand_extra_isize handling
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>
Cc: stable@kernel.org
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7796e2f..71af878 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3545,12 +3545,15 @@ static void ext4_clamp_want_extra_isize(struct super_block *sb)
{
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 == 0) {
- 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))
@@ -3563,10 +3566,10 @@ static void ext4_clamp_want_extra_isize(struct super_block *sb)
}
}
/* 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");
}
