Re: [PATCH 1/4] xfs: Use variable-size array for nameval in xfs_attr_sf_entry

Darrick J. Wong
2020-08-31T15:34:03Z

On Mon, Aug 31, 2020 at 03:04:20PM +0200, Carlos Maiolino wrote:
> nameval is a variable-size array, so, define it as it, and remove all
> the -1 magic number subtractions.
>
> Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
> ---
> fs/xfs/libxfs/xfs_attr_leaf.c | 6 ++----
> fs/xfs/libxfs/xfs_attr_sf.h | 6 +++---
> fs/xfs/libxfs/xfs_da_format.h | 2 +-
> 3 files changed, 6 insertions(+), 8 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
> index 305d4bc073370..7bbc97e0e4d4a 100644
> --- a/fs/xfs/libxfs/xfs_attr_leaf.c
> +++ b/fs/xfs/libxfs/xfs_attr_leaf.c
> @@ -992,7 +992,7 @@ xfs_attr_shortform_allfit(
> return 0;
> if (be16_to_cpu(name_loc->valuelen) >= XFS_ATTR_SF_ENTSIZE_MAX)
> return 0;
> - bytes += sizeof(struct xfs_attr_sf_entry) - 1
> + bytes += sizeof(struct xfs_attr_sf_entry)
> + name_loc->namelen
> + be16_to_cpu(name_loc->valuelen);
> }
> @@ -1036,10 +1036,8 @@ xfs_attr_shortform_verify(
> * struct xfs_attr_sf_entry has a variable length.
> * Check the fixed-offset parts of the structure are
> * within the data buffer.
> - * xfs_attr_sf_entry is defined with a 1-byte variable
> - * array at the end, so we must subtract that off.
> */
> - if (((char *)sfep + sizeof(*sfep) - 1) >= endp)
> + if (((char *)sfep + sizeof(*sfep)) >= endp)
> return __this_address;
>
> /* Don't allow names with known bad length. */
> diff --git a/fs/xfs/libxfs/xfs_attr_sf.h b/fs/xfs/libxfs/xfs_attr_sf.h
> index bb004fb7944a7..d93012a0be4d0 100644
> --- a/fs/xfs/libxfs/xfs_attr_sf.h
> +++ b/fs/xfs/libxfs/xfs_attr_sf.h
> @@ -28,11 +28,11 @@ typedef struct xfs_attr_sf_sort {
> } xfs_attr_sf_sort_t;
>
> #define XFS_ATTR_SF_ENTSIZE_BYNAME(nlen,vlen) /* space name/value uses */ \
> - (((int)sizeof(xfs_attr_sf_entry_t)-1 + (nlen)+(vlen)))
> + (((int)sizeof(xfs_attr_sf_entry_t) + (nlen)+(vlen)))
> #define XFS_ATTR_SF_ENTSIZE_MAX /* max space for name&value */ \
> - ((1 << (NBBY*(int)sizeof(uint8_t))) - 1)
> + (1 << (NBBY*(int)sizeof(uint8_t)))

The maximum space for the name and value is still UINT8_MAX, right?
I don't think this should change to 256.

I also kind of wonder if this should also get changed to be more
direct:

#define XFS_ATTR_SF_ENTSIZE_MAX (UINT8_MAX)

but it's working code, we could/should just leave it be...

> #define XFS_ATTR_SF_ENTSIZE(sfep) /* space an entry uses */ \
> - ((int)sizeof(xfs_attr_sf_entry_t)-1 + (sfep)->namelen+(sfep)->valuelen)
> + ((int)sizeof(xfs_attr_sf_entry_t) + (sfep)->namelen+(sfep)->valuelen)

Can this (and ENTSIZE_BYNAME) use struct_sizeof?

--D

> #define XFS_ATTR_SF_NEXTENTRY(sfep) /* next entry in struct */ \
> ((xfs_attr_sf_entry_t *)((char *)(sfep) + XFS_ATTR_SF_ENTSIZE(sfep)))
> #define XFS_ATTR_SF_TOTSIZE(dp) /* total space in use */ \
> diff --git a/fs/xfs/libxfs/xfs_da_format.h b/fs/xfs/libxfs/xfs_da_format.h
> index 059ac108b1b39..e86185a1165b3 100644
> --- a/fs/xfs/libxfs/xfs_da_format.h
> +++ b/fs/xfs/libxfs/xfs_da_format.h
> @@ -589,7 +589,7 @@ typedef struct xfs_attr_shortform {
> uint8_t namelen; /* actual length of name (no NULL) */
> uint8_t valuelen; /* actual length of value (no NULL) */
> uint8_t flags; /* flags bits (see xfs_attr_leaf.h) */
> - uint8_t nameval[1]; /* name & value bytes concatenated */
> + uint8_t nameval[]; /* name & value bytes concatenated */
> } list[1]; /* variable sized array */
> } xfs_attr_shortform_t;
>
> --
> 2.26.2
>