[PATCH] ocfs2: drop a VLA in ocfs2_orphan_del()

[PATCH] ocfs2: drop a VLA in ocfs2_orphan_del()

[Salvatore Mesoraca]

Avoid a VLA[1] by using a real constant expression instead of a variable.
The compiler should be able to optimize the original code and avoid using
an actual VLA. Anyway this change is useful because it will avoid a false
positive with -Wvla, it might also help the compiler generating better
code.

[1] https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com>
---
 fs/ocfs2/namei.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
index c801edd..41ef356 100644
--- a/fs/ocfs2/namei.c
+++ b/fs/ocfs2/namei.c
@@ -2332,8 +2332,7 @@ int ocfs2_orphan_del(struct ocfs2_super *osb,
 		     struct buffer_head *orphan_dir_bh,
 		     bool dio)
 {
-	const int namelen = OCFS2_DIO_ORPHAN_PREFIX_LEN + OCFS2_ORPHAN_NAMELEN;
-	char name[namelen + 1];
+	char name[OCFS2_DIO_ORPHAN_PREFIX_LEN + OCFS2_ORPHAN_NAMELEN + 1];
 	struct ocfs2_dinode *orphan_fe;
 	int status = 0;
 	struct ocfs2_dir_lookup_result lookup = { NULL, };
-- 
1.9.1

Re: [PATCH] ocfs2: drop a VLA in ocfs2_orphan_del()

[Kees Cook]

On Tue, Mar 13, 2018 at 12:51 PM, Salvatore Mesoraca
<s.mesoraca16@gmail.com> wrote:
> Avoid a VLA[1] by using a real constant expression instead of a variable.
> The compiler should be able to optimize the original code and avoid using
> an actual VLA. Anyway this change is useful because it will avoid a false
> positive with -Wvla, it might also help the compiler generating better
> code.
>
> [1] https://lkml.org/lkml/2018/3/7/621
>
> Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

Andrew, can you take this? It seems the most recent patch to ocfs2
went through your tree...

-Kees

> ---
>  fs/ocfs2/namei.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
> index c801edd..41ef356 100644
> --- a/fs/ocfs2/namei.c
> +++ b/fs/ocfs2/namei.c
> @@ -2332,8 +2332,7 @@ int ocfs2_orphan_del(struct ocfs2_super *osb,
>                      struct buffer_head *orphan_dir_bh,
>                      bool dio)
>  {
> -       const int namelen = OCFS2_DIO_ORPHAN_PREFIX_LEN + OCFS2_ORPHAN_NAMELEN;
> -       char name[namelen + 1];
> +       char name[OCFS2_DIO_ORPHAN_PREFIX_LEN + OCFS2_ORPHAN_NAMELEN + 1];
>         struct ocfs2_dinode *orphan_fe;
>         int status = 0;
>         struct ocfs2_dir_lookup_result lookup = { NULL, };
> --
> 1.9.1
>



-- 
Kees Cook
Pixel Security