[PATCH] riscv: process: fix kernel info leakage

[Conor Dooley]

On Sat, Oct 29, 2022 at 07:34:50PM +0800, Jisheng Zhang wrote:
> thread_struct's s[12] may contain random kernel memory content, which
> may be finally leaked to userspace. This is a security hole. Fix it
> by clearing the s[12] array in thread_struct when fork.
> 
> As for kthread case, it's better to clear the s[12] array as well.
> 
> Fixes: 7db91e57a0ac ("RISC-V: Task implementation")
> Signed-off-by: Jisheng Zhang <jszhang at kernel.org>
> ---
> 
> Previously, it's one of the series of "riscv: entry: further clean up
> and VMAP_STACK fix". This is a fix, so I move it out of the series and
> send it separately

Should this not be carrying a R-b from Guo Ren from that series?
https://lore.kernel.org/linux-riscv/CAJF2gTSdVyAaM12T+7kXAdRPGS4VyuO08X1c7paE-n4Fr8OtRA@mail.gmail.com/
> 
>  arch/riscv/kernel/process.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
> index ceb9ebab6558..52002d54b163 100644
> --- a/arch/riscv/kernel/process.c
> +++ b/arch/riscv/kernel/process.c
> @@ -164,6 +164,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  	unsigned long tls = args->tls;
>  	struct pt_regs *childregs = task_pt_regs(p);
>  
> +	memset(&p->thread.s, 0, sizeof(p->thread.s));
> +
>  	/* p->thread holds context to be restored by __switch_to() */
>  	if (unlikely(args->fn)) {
>  		/* Kernel thread */
> -- 
> 2.37.2
>