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

Submitted by Darrick J. Wong on Oct. 1, 2013, 1:27 a.m.

Details

Message ID 20131001012734.28415.45404.stgit@birch.djwong.org
State Accepted, archived
Headers show

Commit Message

Darrick J. Wong Oct. 1, 2013, 1:27 a.m.
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.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 lib/ext2fs/fileio.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)



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Comments

Lukas Czerner Oct. 7, 2013, 2:02 p.m.
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) &&
> 
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Theodore Ts'o Oct. 8, 2013, 3:52 p.m.
On Mon, Sep 30, 2013 at 06:27:34PM -0700, Darrick J. Wong wrote:
> 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.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

Applied, thanks.

					- Ted
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Patch hide | download patch | download mbox

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) &&