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SubjectRe: [PATCH] randstruct: fix a bug in is_pure_ops_struct()
On Sun, Jul 28, 2019 at 12:58:41AM +0900, Joonwon Kang wrote:
> Before this, there were false negatives in the case where a struct
> contains other structs which contain only function pointers because
> of unreachable code in is_pure_ops_struct().

Ah, very true. Something like:

struct internal {
void (*callback)(void);
};

struct wrapper {
struct internal foo;
void (*other_callback)(void);
};

would have not been detected as is_pure_ops_struct()?

How did you notice this? (Are there cases of this in the kernel?)

> Signed-off-by: Joonwon Kang <kjw1627@gmail.com>

Applied; thanks!

-Kees

> ---
> scripts/gcc-plugins/randomize_layout_plugin.c | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c b/scripts/gcc-plugins/randomize_layout_plugin.c
> index 6d5bbd31db7f..a123282a4fcd 100644
> --- a/scripts/gcc-plugins/randomize_layout_plugin.c
> +++ b/scripts/gcc-plugins/randomize_layout_plugin.c
> @@ -443,13 +443,12 @@ static int is_pure_ops_struct(const_tree node)
> if (node == fieldtype)
> continue;
>
> - if (!is_fptr(fieldtype))
> - return 0;
> -
> - if (code != RECORD_TYPE && code != UNION_TYPE)
> - continue;
> + if (code == RECORD_TYPE || code == UNION_TYPE) {
> + if (!is_pure_ops_struct(fieldtype))
> + return 0;
> + }
>
> - if (!is_pure_ops_struct(fieldtype))
> + if (!is_fptr(fieldtype))
> return 0;
> }
>
> --
> 2.17.1
>

--
Kees Cook

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