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>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 516faa280ceda8d8035363f63153bbdac4901002..d691d1783ed62db8adf8a2341070b79416f42ca0 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5912,8 +5912,23 @@ 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 dd654e53ba3d982d99c05b2336dd4de9132b0978..73578359d45163d570e3060a3ee0102b4dae9fa4 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3555,12 +3555,15 @@ 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))
@@ -3573,10 +3576,10 @@ 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");
        }