Re: [PATCH 08/31] libext2fs: Fix off-by-one error in file truncation

Lukáš Czerner
2013-10-07T14:02:12Z

On Mon, 30 Sep 2013, Darrick J. Wong wrote:

> Date: Mon, 30 Sep 2013 18:27:34 -0700
> From: Darrick J. Wong <darrick.wong@oracle.com>
> To: tytso@mit.edu, darrick.wong@oracle.com
> Cc: linux-ext4@vger.kernel.org
> Subject: [PATCH 08/31] libext2fs: Fix off-by-one error in file truncation
>
> When told to truncate a file, ext2fs_file_set_size2 should start with the first
> block past the end of the file. The current calculation jumps one more block
> ahead, with the result that it fails to hack off the last block. Adding
> blocksize-1 and dividing is sufficient to find the last block.

Looks good.

Reviewed-by: Lukas Czerner <lczerner@redhat.com>

>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
> lib/ext2fs/fileio.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>
> diff --git a/lib/ext2fs/fileio.c b/lib/ext2fs/fileio.c
> index ae5cbf1..d875630 100644
> --- a/lib/ext2fs/fileio.c
> +++ b/lib/ext2fs/fileio.c
> @@ -384,10 +384,10 @@ errcode_t ext2fs_file_set_size2(ext2_file_t file, ext2_off64_t size)
> EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
>
> truncate_block = ((size + file->fs->blocksize - 1) >>
> - EXT2_BLOCK_SIZE_BITS(file->fs->super)) + 1;
> + EXT2_BLOCK_SIZE_BITS(file->fs->super));
> old_size = EXT2_I_SIZE(&file->inode);
> old_truncate = ((old_size + file->fs->blocksize - 1) >>
> - EXT2_BLOCK_SIZE_BITS(file->fs->super)) + 1;
> + EXT2_BLOCK_SIZE_BITS(file->fs->super));
>
> /* If we're writing a large file, set the large_file flag */
> if (LINUX_S_ISREG(file->inode.i_mode) &&
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>