[RFC][PATCH v4 04/09] ext2: use common file type conversion

[RFC][PATCH v4 04/09] ext2: use common file type conversion

[Phillip Potter]

Deduplicate the ext2 file type conversion implementation - file systems
that use the same file types as defined by POSIX do not need to define
their own versions and can use the common helper functions decared in
fs_types.h and implemented in fs_types.c

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
---
 fs/ext2/dir.c | 49 ++++++++++++++++++++-----------------------------
 1 file changed, 20 insertions(+), 29 deletions(-)

diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index 3b8114def693..bd30fe266373 100644
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -252,33 +252,24 @@ ext2_validate_entry(char *base, unsigned offset, unsigned mask)
 	return (char *)p - base;
 }
 
-static unsigned char ext2_filetype_table[EXT2_FT_MAX] = {
-	[EXT2_FT_UNKNOWN]	= DT_UNKNOWN,
-	[EXT2_FT_REG_FILE]	= DT_REG,
-	[EXT2_FT_DIR]		= DT_DIR,
-	[EXT2_FT_CHRDEV]	= DT_CHR,
-	[EXT2_FT_BLKDEV]	= DT_BLK,
-	[EXT2_FT_FIFO]		= DT_FIFO,
-	[EXT2_FT_SOCK]		= DT_SOCK,
-	[EXT2_FT_SYMLINK]	= DT_LNK,
-};
-
-#define S_SHIFT 12
-static unsigned char ext2_type_by_mode[S_IFMT >> S_SHIFT] = {
-	[S_IFREG >> S_SHIFT]	= EXT2_FT_REG_FILE,
-	[S_IFDIR >> S_SHIFT]	= EXT2_FT_DIR,
-	[S_IFCHR >> S_SHIFT]	= EXT2_FT_CHRDEV,
-	[S_IFBLK >> S_SHIFT]	= EXT2_FT_BLKDEV,
-	[S_IFIFO >> S_SHIFT]	= EXT2_FT_FIFO,
-	[S_IFSOCK >> S_SHIFT]	= EXT2_FT_SOCK,
-	[S_IFLNK >> S_SHIFT]	= EXT2_FT_SYMLINK,
-};
-
 static inline void ext2_set_de_type(ext2_dirent *de, struct inode *inode)
 {
-	umode_t mode = inode->i_mode;
+	/*
+	 * compile-time asserts that generic FT_x types still match
+	 * EXT2_FT_x types
+	 */
+	BUILD_BUG_ON(EXT2_FT_UNKNOWN != FT_UNKNOWN);
+	BUILD_BUG_ON(EXT2_FT_REG_FILE != FT_REG_FILE);
+	BUILD_BUG_ON(EXT2_FT_DIR != FT_DIR);
+	BUILD_BUG_ON(EXT2_FT_CHRDEV != FT_CHRDEV);
+	BUILD_BUG_ON(EXT2_FT_BLKDEV != FT_BLKDEV);
+	BUILD_BUG_ON(EXT2_FT_FIFO != FT_FIFO);
+	BUILD_BUG_ON(EXT2_FT_SOCK != FT_SOCK);
+	BUILD_BUG_ON(EXT2_FT_SYMLINK != FT_SYMLINK);
+	BUILD_BUG_ON(EXT2_FT_MAX != FT_MAX);
+
 	if (EXT2_HAS_INCOMPAT_FEATURE(inode->i_sb, EXT2_FEATURE_INCOMPAT_FILETYPE))
-		de->file_type = ext2_type_by_mode[(mode & S_IFMT)>>S_SHIFT];
+		de->file_type = fs_umode_to_ftype(inode->i_mode);
 	else
 		de->file_type = 0;
 }
@@ -293,14 +284,14 @@ ext2_readdir(struct file *file, struct dir_context *ctx)
 	unsigned long n = pos >> PAGE_SHIFT;
 	unsigned long npages = dir_pages(inode);
 	unsigned chunk_mask = ~(ext2_chunk_size(inode)-1);
-	unsigned char *types = NULL;
 	bool need_revalidate = !inode_eq_iversion(inode, file->f_version);
+	bool has_filetype;
 
 	if (pos > inode->i_size - EXT2_DIR_REC_LEN(1))
 		return 0;
 
-	if (EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_FILETYPE))
-		types = ext2_filetype_table;
+	has_filetype =
+		EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_FILETYPE);
 
 	for ( ; n < npages; n++, offset = 0) {
 		char *kaddr, *limit;
@@ -335,8 +326,8 @@ ext2_readdir(struct file *file, struct dir_context *ctx)
 			if (de->inode) {
 				unsigned char d_type = DT_UNKNOWN;
 
-				if (types && de->file_type < EXT2_FT_MAX)
-					d_type = types[de->file_type];
+				if (has_filetype)
+					d_type = fs_ftype_to_dtype(de->file_type);
 
 				if (!dir_emit(ctx, de->name, de->name_len,
 						le32_to_cpu(de->inode),
-- 
2.19.1

Re: [RFC][PATCH v4 04/09] ext2: use common file type conversion

[Jan Kara]

On Wed 21-11-18 19:06:53, Phillip Potter wrote:
> Deduplicate the ext2 file type conversion implementation - file systems
> that use the same file types as defined by POSIX do not need to define
> their own versions and can use the common helper functions decared in
> fs_types.h and implemented in fs_types.c
> 
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> Signed-off-by: Phillip Potter <phil@philpotter.co.uk>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/ext2/dir.c | 49 ++++++++++++++++++++-----------------------------
>  1 file changed, 20 insertions(+), 29 deletions(-)
> 
> diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
> index 3b8114def693..bd30fe266373 100644
> --- a/fs/ext2/dir.c
> +++ b/fs/ext2/dir.c
> @@ -252,33 +252,24 @@ ext2_validate_entry(char *base, unsigned offset, unsigned mask)
>  	return (char *)p - base;
>  }
>  
> -static unsigned char ext2_filetype_table[EXT2_FT_MAX] = {
> -	[EXT2_FT_UNKNOWN]	= DT_UNKNOWN,
> -	[EXT2_FT_REG_FILE]	= DT_REG,
> -	[EXT2_FT_DIR]		= DT_DIR,
> -	[EXT2_FT_CHRDEV]	= DT_CHR,
> -	[EXT2_FT_BLKDEV]	= DT_BLK,
> -	[EXT2_FT_FIFO]		= DT_FIFO,
> -	[EXT2_FT_SOCK]		= DT_SOCK,
> -	[EXT2_FT_SYMLINK]	= DT_LNK,
> -};
> -
> -#define S_SHIFT 12
> -static unsigned char ext2_type_by_mode[S_IFMT >> S_SHIFT] = {
> -	[S_IFREG >> S_SHIFT]	= EXT2_FT_REG_FILE,
> -	[S_IFDIR >> S_SHIFT]	= EXT2_FT_DIR,
> -	[S_IFCHR >> S_SHIFT]	= EXT2_FT_CHRDEV,
> -	[S_IFBLK >> S_SHIFT]	= EXT2_FT_BLKDEV,
> -	[S_IFIFO >> S_SHIFT]	= EXT2_FT_FIFO,
> -	[S_IFSOCK >> S_SHIFT]	= EXT2_FT_SOCK,
> -	[S_IFLNK >> S_SHIFT]	= EXT2_FT_SYMLINK,
> -};
> -
>  static inline void ext2_set_de_type(ext2_dirent *de, struct inode *inode)
>  {
> -	umode_t mode = inode->i_mode;
> +	/*
> +	 * compile-time asserts that generic FT_x types still match
> +	 * EXT2_FT_x types
> +	 */
> +	BUILD_BUG_ON(EXT2_FT_UNKNOWN != FT_UNKNOWN);
> +	BUILD_BUG_ON(EXT2_FT_REG_FILE != FT_REG_FILE);
> +	BUILD_BUG_ON(EXT2_FT_DIR != FT_DIR);
> +	BUILD_BUG_ON(EXT2_FT_CHRDEV != FT_CHRDEV);
> +	BUILD_BUG_ON(EXT2_FT_BLKDEV != FT_BLKDEV);
> +	BUILD_BUG_ON(EXT2_FT_FIFO != FT_FIFO);
> +	BUILD_BUG_ON(EXT2_FT_SOCK != FT_SOCK);
> +	BUILD_BUG_ON(EXT2_FT_SYMLINK != FT_SYMLINK);
> +	BUILD_BUG_ON(EXT2_FT_MAX != FT_MAX);
> +
>  	if (EXT2_HAS_INCOMPAT_FEATURE(inode->i_sb, EXT2_FEATURE_INCOMPAT_FILETYPE))
> -		de->file_type = ext2_type_by_mode[(mode & S_IFMT)>>S_SHIFT];
> +		de->file_type = fs_umode_to_ftype(inode->i_mode);
>  	else
>  		de->file_type = 0;
>  }
> @@ -293,14 +284,14 @@ ext2_readdir(struct file *file, struct dir_context *ctx)
>  	unsigned long n = pos >> PAGE_SHIFT;
>  	unsigned long npages = dir_pages(inode);
>  	unsigned chunk_mask = ~(ext2_chunk_size(inode)-1);
> -	unsigned char *types = NULL;
>  	bool need_revalidate = !inode_eq_iversion(inode, file->f_version);
> +	bool has_filetype;
>  
>  	if (pos > inode->i_size - EXT2_DIR_REC_LEN(1))
>  		return 0;
>  
> -	if (EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_FILETYPE))
> -		types = ext2_filetype_table;
> +	has_filetype =
> +		EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_FILETYPE);
>  
>  	for ( ; n < npages; n++, offset = 0) {
>  		char *kaddr, *limit;
> @@ -335,8 +326,8 @@ ext2_readdir(struct file *file, struct dir_context *ctx)
>  			if (de->inode) {
>  				unsigned char d_type = DT_UNKNOWN;
>  
> -				if (types && de->file_type < EXT2_FT_MAX)
> -					d_type = types[de->file_type];
> +				if (has_filetype)
> +					d_type = fs_ftype_to_dtype(de->file_type);
>  
>  				if (!dir_emit(ctx, de->name, de->name_len,
>  						le32_to_cpu(de->inode),
> -- 
> 2.19.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [RFC][PATCH v4 04/09] ext2: use common file type conversion

[Amir Goldstein]

On Thu, Nov 22, 2018 at 1:40 PM Jan Kara <jack@suse.cz> wrote:
>
> On Wed 21-11-18 19:06:53, Phillip Potter wrote:
> > Deduplicate the ext2 file type conversion implementation - file systems
> > that use the same file types as defined by POSIX do not need to define
> > their own versions and can use the common helper functions decared in
> > fs_types.h and implemented in fs_types.c
> >
> > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
>
> Looks good. You can add:
>
> Reviewed-by: Jan Kara <jack@suse.cz>

Jan,

As you know, Al probably has bigger fish to fry at the moment.
Will you take this patch along with patch #1 through your tree?
Other fs maintainers could apply patches on next cycle (or coordinate
they pull request with you).

If you would agree to that, I suggest to copy the following section
from the cover letter into the ext2 patch:

The current implementation has a lurking out-of-bounds access
bug to the ext2_type_by_mode array.
The array is defined with size S_IFMT >> S_SHIFT, so 15.
This means that it is possible with a malformed inode to
get an index of 15, as the array is always accessed with:
ext2_type_by_mode[(mode & S_IFMT)>>S_SHIFT];

Thanks,
Amir.

Re: [RFC][PATCH v4 04/09] ext2: use common file type conversion

[Phillip Potter]

On Thu, Nov 22, 2018 at 12:40:23PM +0100, Jan Kara wrote:
> On Wed 21-11-18 19:06:53, Phillip Potter wrote:
> > Deduplicate the ext2 file type conversion implementation - file systems
> > that use the same file types as defined by POSIX do not need to define
> > their own versions and can use the common helper functions decared in
> > fs_types.h and implemented in fs_types.c
> > 
> > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
> 
> Looks good. You can add:
> 
> Reviewed-by: Jan Kara <jack@suse.cz>
> 
> 								Honza

Dear Jan,

Thank you for reviewing this patch, and for all the others too. Much
appreciated.

Regards,
Phil

Re: [RFC][PATCH v4 04/09] ext2: use common file type conversion

[Jan Kara]

On Thu 22-11-18 14:47:39, Amir Goldstein wrote:
> On Thu, Nov 22, 2018 at 1:40 PM Jan Kara <jack@suse.cz> wrote:
> >
> > On Wed 21-11-18 19:06:53, Phillip Potter wrote:
> > > Deduplicate the ext2 file type conversion implementation - file systems
> > > that use the same file types as defined by POSIX do not need to define
> > > their own versions and can use the common helper functions decared in
> > > fs_types.h and implemented in fs_types.c
> > >
> > > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > > Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
> >
> > Looks good. You can add:
> >
> > Reviewed-by: Jan Kara <jack@suse.cz>
> 
> Jan,
> 
> As you know, Al probably has bigger fish to fry at the moment.
> Will you take this patch along with patch #1 through your tree?
> Other fs maintainers could apply patches on next cycle (or coordinate
> they pull request with you).
> 
> If you would agree to that, I suggest to copy the following section
> from the cover letter into the ext2 patch:
> 
> The current implementation has a lurking out-of-bounds access
> bug to the ext2_type_by_mode array.
> The array is defined with size S_IFMT >> S_SHIFT, so 15.
> This means that it is possible with a malformed inode to
> get an index of 15, as the array is always accessed with:
> ext2_type_by_mode[(mode & S_IFMT)>>S_SHIFT];

Yes, I will do that.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR