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References: <20221029113450.4027-1-jszhang@kernel.org>
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From:   Guo Ren <guoren@kernel.org>
Date:   Sun, 30 Oct 2022 08:03:33 +0800
Message-ID: <CAJF2gTSqUtU77HvEsQi8+akod4Fn1pEe2REH2nae39dK2VsacA@mail.gmail.com>
Subject: Re: [PATCH] riscv: process: fix kernel info leakage
To:     Jisheng Zhang <jszhang@kernel.org>
Cc:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
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On Sat, Oct 29, 2022 at 7:44 PM Jisheng Zhang <jszhang@kernel.org> 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@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
>
>  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));
Tested-by: Guo Ren <guoren@kernel.org>

> +
>         /* p->thread holds context to be restored by __switch_to() */
>         if (unlikely(args->fn)) {
>                 /* Kernel thread */
> --
> 2.37.2
>


-- 
Best Regards
 Guo Ren