Re: [PATCH 06/37] libext2fs: Add inode checksum support

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On 2011-08-31, at 6:35 PM, "Darrick J. Wong" <djwong@xxxxxxxxxx> wrote:

> This patch adds the ability for the libext2fs functions to read and write the
> inode checksum.  It also fixes a few fields that were omitted from the byte
> swapping routines.
> 
> Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> ---
> lib/ext2fs/csum.c         |   59 +++++++++++++++++++++++++++++++++++++++++++++
> lib/ext2fs/ext2_err.et.in |    9 +++++++
> lib/ext2fs/ext2_fs.h      |    4 ++-
> lib/ext2fs/ext2fs.h       |    6 +++++
> lib/ext2fs/inode.c        |   20 +++++++++++++++
> lib/ext2fs/swapfs.c       |   10 ++++++--
> 6 files changed, 104 insertions(+), 4 deletions(-)
> 
> 
> diff --git a/lib/ext2fs/csum.c b/lib/ext2fs/csum.c
> index 2fece68..57adc4c 100644
> --- a/lib/ext2fs/csum.c
> +++ b/lib/ext2fs/csum.c
> @@ -29,6 +29,65 @@
> #define STATIC static
> #endif
> 
> +__u32 ext2fs_inode_csum(ext2_filsys fs, ext2_ino_t inum,
> +            struct ext2_inode_large *inode)
> +{
> +    struct ext2_inode_large *desc = inode;
> +    int offset = offsetof(struct ext2_inode_large, i_checksum);
> +    int extra_size = inode->i_extra_isize;
> +    size_t size = fs->super->s_inode_size;
> +    __u32 crc = 0;
> +
> +    if (size < EXT2_GOOD_OLD_INODE_SIZE + extra_size)
> +        printf("ERROR: inode %d size %d != extra_size %d!\n", inum,
> +               size, extra_size + EXT2_GOOD_OLD_INODE_SIZE);

This shouldn't have to be checked for every inode checksum. If the checksum is covering the whole inode size then this is a constant size, and e2fsck is already checking the value of i_extra_isize. 

> +    if (fs->super->s_creator_os != EXT2_OS_LINUX)
> +        return 0;
> +
> +    if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
> +                    EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
> +
> +        return 0;
> +
> +#ifdef WORDS_BIGENDIAN
> +    char buf[EXT2_INODE_CORE_SIZE(fs->super)];
> +    struct ext2_inode_large *swabinode = (struct ext2_inode_large *)buf;
> +
> +    /* Have to swab back to little-endian to do the checksum */
> +    memcpy(swabinode, inode, size);
> +    ext2fs_swap_inode_full(fs, swabinode, swabinode, 1, size);
> +    desc = swabinode;
> +#endif
> +    inum = ext2fs_cpu_to_le32(inum);
> +    crc = crc32c_le(~0, fs->super->s_uuid, sizeof(fs->super->s_uuid));
> +    crc = crc32c_le(crc, (char *)&inum, sizeof(inum));
> +    crc = crc32c_le(crc, (char *)desc, offset);
> +    offset += sizeof(inode->i_checksum); /* skip checksum */
> +    crc = crc32c_le(crc, (char *)desc + offset,
> +               EXT2_GOOD_OLD_INODE_SIZE + extra_size - offset);
> +    return crc;
> +}
> +
> +int ext2fs_inode_csum_verify(ext2_filsys fs, ext2_ino_t inum,
> +                 struct ext2_inode_large *inode)
> +{
> +    if (fs->super->s_creator_os == EXT2_OS_LINUX &&
> +        EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
> +                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM) &&
> +        (inode->i_checksum != ext2fs_inode_csum(fs, inum, inode)))
> +        return 0;
> +    return 1;
> +}
> +
> +void ext2fs_inode_csum_set(ext2_filsys fs, ext2_ino_t inum,
> +               struct ext2_inode_large *inode)
> +{
> +    if (fs->super->s_creator_os != EXT2_OS_LINUX)
> +        return;
> +    inode->i_checksum = ext2fs_inode_csum(fs, inum, inode);
> +}
> +
> STATIC __u16 ext2fs_group_desc_csum(ext2_filsys fs, dgrp_t group)
> {
>    __u16 crc = 0;
> diff --git a/lib/ext2fs/ext2_err.et.in b/lib/ext2fs/ext2_err.et.in
> index 995ddc3..31c8fe1 100644
> --- a/lib/ext2fs/ext2_err.et.in
> +++ b/lib/ext2fs/ext2_err.et.in
> @@ -422,4 +422,13 @@ ec    EXT2_NO_MTAB_FILE,
> ec    EXT2_ET_CANT_USE_LEGACY_BITMAPS,
>    "Filesystem too large to use legacy bitmaps"
> 
> +ec    EXT2_ET_INODE_CSUM_INVALID,
> +    "Inode checksum is incorrect"
> +
> +ec    EXT2_ET_INODE_CORRUPT,
> +    "Inode checksum indicates corruption"
> +
> +ec    EXT2_ET_INODE_CSUM_NONZERO,
> +    "Inode checksum should not be set"
> +
>    end
> diff --git a/lib/ext2fs/ext2_fs.h b/lib/ext2fs/ext2_fs.h
> index ae7662e..1f08673 100644
> --- a/lib/ext2fs/ext2_fs.h
> +++ b/lib/ext2fs/ext2_fs.h
> @@ -362,7 +362,7 @@ struct ext2_inode_large {
>            __u16    l_i_file_acl_high;
>            __u16    l_i_uid_high;    /* these 2 fields    */
>            __u16    l_i_gid_high;    /* were reserved2[0] */
> -            __u32    l_i_reserved2;
> +            __u32    l_i_checksum;    /* crc32c(uuid+inum+inode) */
>        } linux2;
>        struct {
>            __u8    h_i_frag;    /* Fragment number */
> @@ -393,7 +393,7 @@ struct ext2_inode_large {
> #define i_gid_low    i_gid
> #define i_uid_high    osd2.linux2.l_i_uid_high
> #define i_gid_high    osd2.linux2.l_i_gid_high
> -#define i_reserved2    osd2.linux2.l_i_reserved2
> +#define i_checksum    osd2.linux2.l_i_checksum
> #else
> #if defined(__GNU__)
> 
> diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
> index e571508..db8b28b 100644
> --- a/lib/ext2fs/ext2fs.h
> +++ b/lib/ext2fs/ext2fs.h
> @@ -892,6 +892,12 @@ extern __u32 crc32c_be(__u32 crc, unsigned char const *p, size_t len);
> extern __u32 crc32c_le(__u32 crc, unsigned char const *p, size_t len);
> 
> /* csum.c */
> +extern __u32 ext2fs_inode_csum(ext2_filsys fs, ext2_ino_t inum,
> +                  struct ext2_inode_large *inode);
> +extern void ext2fs_inode_csum_set(ext2_filsys fs, ext2_ino_t inum,
> +                  struct ext2_inode_large *inode);
> +extern int ext2fs_inode_csum_verify(ext2_filsys fs, ext2_ino_t inum,
> +                    struct ext2_inode_large *inode);
> extern void ext2fs_group_desc_csum_set(ext2_filsys fs, dgrp_t group);
> extern int ext2fs_group_desc_csum_verify(ext2_filsys fs, dgrp_t group);
> extern errcode_t ext2fs_set_gdt_csum(ext2_filsys fs);
> diff --git a/lib/ext2fs/inode.c b/lib/ext2fs/inode.c
> index 76893fd..0789505 100644
> --- a/lib/ext2fs/inode.c
> +++ b/lib/ext2fs/inode.c
> @@ -509,6 +509,12 @@ errcode_t ext2fs_get_next_inode_full(ext2_inode_scan scan, ext2_ino_t *ino,
>    if (EXT2_INODE_SIZE(scan->fs->super) == EXT2_GOOD_OLD_INODE_SIZE)
>        inode->i_extra_isize = 0;
> 
> +    /* Verify the inode checksum. */
> +    if (!(scan->fs->flags & EXT2_FLAG_IGNORE_CSUM_ERRORS) &&
> +        !ext2fs_inode_csum_verify(scan->fs, scan->current_inode, inode))
> +        return EXT2_ET_INODE_CSUM_INVALID;
> +
> +
>    scan->inodes_left--;
>    scan->current_inode++;
>    *ino = scan->current_inode;
> @@ -617,6 +623,10 @@ errcode_t ext2fs_read_inode_full(ext2_filsys fs, ext2_ino_t ino,
>                   (struct ext2_inode_large *) inode,
>                   0, bufsize);
> #endif
> +    /* Verify the inode checksum. */
> +    if (!(fs->flags & EXT2_FLAG_IGNORE_CSUM_ERRORS) &&
> +        !ext2fs_inode_csum_verify(fs, ino, inode))
> +        return EXT2_ET_INODE_CSUM_INVALID;
> 
>    /* Update the inode cache */
>    fs->icache->cache_last = (fs->icache->cache_last + 1) %
> @@ -685,6 +695,16 @@ errcode_t ext2fs_write_inode_full(ext2_filsys fs, ext2_ino_t ino,
>        w_inode = &temp_inode;
>    memset(w_inode, 0, length);
> 
> +    /*
> +     * If inode checksum enabled, ensure that we actually have the whole
> +     * inode in memory.
> +     */
> +    if (EXT2_INODE_SIZE(fs->super) > EXT2_GOOD_OLD_INODE_SIZE &&
> +        bufsize <= EXT2_GOOD_OLD_INODE_SIZE) {
> +        fprintf(stderr, "inode %d has a too-short buffer!\n", ino);
> +        abort();
> +    }
> +    ext2fs_inode_csum_set(fs, ino, inode);
> #ifdef WORDS_BIGENDIAN
>    ext2fs_swap_inode_full(fs, w_inode, inode, 1, bufsize);
> #else
> diff --git a/lib/ext2fs/swapfs.c b/lib/ext2fs/swapfs.c
> index 517f1d7..df604ba 100644
> --- a/lib/ext2fs/swapfs.c
> +++ b/lib/ext2fs/swapfs.c
> @@ -244,8 +244,7 @@ void ext2fs_swap_inode_full(ext2_filsys fs, struct ext2_inode_large *t,
>          ext2fs_swab16 (f->osd2.linux2.l_i_uid_high);
>        t->osd2.linux2.l_i_gid_high =
>          ext2fs_swab16 (f->osd2.linux2.l_i_gid_high);
> -        t->osd2.linux2.l_i_reserved2 =
> -            ext2fs_swab32(f->osd2.linux2.l_i_reserved2);
> +        t->i_checksum = ext2fs_swab32(f->i_checksum);
>        break;
>    case EXT2_OS_HURD:
>        t->osd1.hurd1.h_i_translator =
> @@ -279,6 +278,13 @@ void ext2fs_swap_inode_full(ext2_filsys fs, struct ext2_inode_large *t,
>        return;
>    }
> 
> +    t->i_ctime_extra = ext2fs_swab32(f->i_ctime_extra);
> +    t->i_mtime_extra = ext2fs_swab32(f->i_mtime_extra);
> +    t->i_atime_extra = ext2fs_swab32(f->i_atime_extra);
> +    t->i_crtime = ext2fs_swab32(f->i_crtime);
> +    t->i_crtime_extra = ext2fs_swab32(f->i_crtime_extra);
> +    t->i_version_hi = ext2fs_swab32(f->i_version_hi);
> +
>    i = EXT2_GOOD_OLD_INODE_SIZE + extra_isize + sizeof(__u32);
>    if (bufsize < (int) i)
>        return; /* no space for EA magic */
> 
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