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    Subject[PATCH 5.3 132/135] ext4: add more paranoia checking in ext4_expand_extra_isize handling
    Date
    From: Theodore Ts'o <tytso@mit.edu>

    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>

    ---
    fs/ext4/inode.c | 15 +++++++++++++++
    fs/ext4/super.c | 21 ++++++++++++---------
    2 files changed, 27 insertions(+), 9 deletions(-)

    --- a/fs/ext4/inode.c
    +++ b/fs/ext4/inode.c
    @@ -5942,8 +5942,23 @@ static int __ext4_expand_extra_isize(str
    {
    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);
    --- a/fs/ext4/super.c
    +++ b/fs/ext4/super.c
    @@ -3544,12 +3544,15 @@ static void ext4_clamp_want_extra_isize(
    {
    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))
    @@ -3562,10 +3565,10 @@ static void ext4_clamp_want_extra_isize(
    }
    }
    /* 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");
    }

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