libext2fs: only use override function when reading an 128 byte inode

The ext2fs_read_inode_full() function should not use fs->read_inode()
if the caller has requested more than the base 128 byte inode
structure and the inode size is greater than 128 bytes.  Otherwise the
caller won't get all of the bytes that they were asking for, since
there's no way for the fs->read_inode override function can know what
the size of the buffer passed to ext2fs_read_inode_full().

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
 lib/ext2fs/inode.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Looks Good,

Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>

On Sun, Apr 21, 2013 at 11:56:09PM -0400, Theodore Ts'o wrote:
> The ext2fs_read_inode_full() function should not use fs->read_inode()
> if the caller has requested more than the base 128 byte inode
> structure and the inode size is greater than 128 bytes.  Otherwise the
> caller won't get all of the bytes that they were asking for, since
> there's no way for the fs->read_inode override function can know what
> the size of the buffer passed to ext2fs_read_inode_full().
> 
> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
> ---
>  lib/ext2fs/inode.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/ext2fs/inode.c b/lib/ext2fs/inode.c
> index 77fc447..fd72d4c 100644
> --- a/lib/ext2fs/inode.c
> +++ b/lib/ext2fs/inode.c
> @@ -533,7 +533,9 @@ errcode_t ext2fs_read_inode_full(ext2_filsys fs, ext2_ino_t ino,
>  	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
>  
>  	/* Check to see if user has an override function */
> -	if (fs->read_inode) {
> +	if (fs->read_inode &&
> +	    ((bufsize == sizeof(struct ext2_inode)) ||
> +	     (EXT2_INODE_SIZE(fs->super) == sizeof(struct ext2_inode)))) {
>  		retval = (fs->read_inode)(fs, ino, inode);
>  		if (retval != EXT2_ET_CALLBACK_NOTHANDLED)
>  			return retval;
> -- 
> 1.7.12.rc0.22.gcdd159b
> 
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