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/inode.c b/fs/ext4/inode.c
index 381813205f99a3d8b82f5df835558a5e35c44ec8..c6e3fe287b50b5354138df4738d08da6e61340f8 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5569,8 +5569,23 @@ static int __ext4_expand_extra_isize(struct inode *inode,
 {
        struct ext4_inode *raw_inode;
        struct ext4_xattr_ibody_header *header;
+       unsigned int inode_size = EXT4_INODE_SIZE(inode->i_sb);
+       struct ext4_inode_info *ei = EXT4_I(inode);
        int error;
 
+       /* this was checked at iget time, but double check for good measure */
+       if ((EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize > inode_size) ||
+           (ei->i_extra_isize & 3)) {
+               EXT4_ERROR_INODE(inode, "bad extra_isize %u (inode size %u)",
+                                ei->i_extra_isize,
+                                EXT4_INODE_SIZE(inode->i_sb));
+               return -EFSCORRUPTED;
+       }
+       if ((new_extra_isize < ei->i_extra_isize) ||
+           (new_extra_isize < 4) ||
+           (new_extra_isize > inode_size - EXT4_GOOD_OLD_INODE_SIZE))
+               return -EINVAL; /* Should never happen */
+
        raw_inode = ext4_raw_inode(iloc);
 
        header = IHDR(inode, raw_inode);

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7796e2ffc29425444d7eb65ecf48c88b572b675e..71af8780d4ee118c2ef93e0d6ae3e988f154bd46 100644 (file)
--- 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");
        }