Hi,
On Sat, Nov 25, 2023 at 03:33:58PM -0600, Gustavo A. R. Silva wrote:
> Previously, one-element and zero-length arrays were treated as true
> flexible arrays, even though they are actually "fake" flex arrays.
> The __randomize_layout would leave them untouched at the end of the
> struct, similarly to proper C99 flex-array members.
>
> However, this approach changed with commit 1ee60356c2dc ("gcc-plugins:
> randstruct: Only warn about true flexible arrays"). Now, only C99
> flexible-array members will remain untouched at the end of the struct,
> while one-element and zero-length arrays will be subject to randomization.
>
> Fix a `__randomize_layout` crash in `struct neighbour` by transforming
> zero-length array `primary_key` into a proper C99 flexible-array member.
>
> Fixes: 1ee60356c2dc ("gcc-plugins: randstruct: Only warn about true flexible
> arrays")
> Closes:
> https://lore.kernel.org/linux-hardening/[email protected]/
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
> ---
> include/net/neighbour.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/net/neighbour.h b/include/net/neighbour.h
> index 07022bb0d44d..0d28172193fa 100644
> --- a/include/net/neighbour.h
> +++ b/include/net/neighbour.h
> @@ -162,7 +162,7 @@ struct neighbour {
> struct rcu_head rcu;
> struct net_device *dev;
> netdevice_tracker dev_tracker;
> - u8 primary_key[0];
> + u8 primary_key[];
> } __randomize_layout;
>
> struct neigh_ops {
Fixes the crash for me!
Tested-by: Joey Gouly <[email protected]>
