Re: [PATCH] 2.6.35.4: Fixed simple warning (array subscript is above array bounds)

Alex Elder
2010-09-16T16:41:16Z

On Thu, 2010-09-02 at 02:10 -0700, Poyo VL wrote:
> From: Ionut Gabriel Popescu <poyo_vl@yahoo.com>
>
> When I tried to compile, I got the following warning:
> fs/xfs/xfs_dir2_block.c: In function ‘xfs_dir2_sf_to_block’:
> fs/xfs/xfs_dir2_block.c:1153:26: warning: array subscript is above array bounds
> The code (fs/xfs/xfs_dir2_block.c line 1153) is:
> dep->name[0] = dep->name[1] = '.';
> dep is a pointer to a xfs_dir2_data_entry_t structure where name is defined as:
> __u8 name[1]; /* name bytes, no null */
> So it is a single element array, name[0] not also name[1] so I got that warning.
> Patching is a simple replacement of 1 with 2.

It looks to me like this will work. But I would like
a second opinion on that before I commit this change.

An xfs_dir2_data_entry structure is defined the way
it is to be informative; its physical representation
is different when it's actually used. The name array
is sized based on the actual name length, and the tag
lies somewhere after that--at the very end of the
(dynamically-sized) data entry.

Additionally, the alignment of the overall structure
will be 64 bits because of hte inumber field. Expanding
the name field by another byte will not change that.

So I think this change is OK. Can anyone else
back me up?

Reviewed-by: Alex Elder <aelder@sgi.com>

> Signed-off-by: Ionut Gabriel Popescu <poyo_vl@yahoo.com>
> ---
>
> --- a/fs/xfs/xfs_dir2_data.h 2010-09-02 11:13:11.632007536 +0300
> +++ b/fs/xfs/xfs_dir2_data.h 2010-09-02 11:13:28.080006488 +0300
> @@ -87,7 +87,7 @@
> typedef struct xfs_dir2_data_entry {
> __be64 inumber; /* inode number */
> __u8 namelen; /* name length */
> - __u8 name[1]; /* name bytes, no null */
> + __u8 name[2]; /* name bytes, no null */
> /* variable offset */
> __be16 tag; /* starting offset of us */
> } xfs_dir2_data_entry_t;
>
>
>