linux-kernel - Re: [PATCH] x86/ptrace: Mark expected switch fall-through

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Date:   Mon, 5 Aug 2019 13:19:20 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Oleg Nesterov <oleg@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/ptrace: Mark expected switch fall-through

On Mon, Aug 05, 2019 at 02:56:54PM -0500, Gustavo A. R. Silva wrote:
> Mark switch cases where we are expecting to fall through.
> 
> Fix the following warning (Building: allnoconfig i386):
> 
> arch/x86/kernel/ptrace.c:202:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    if (unlikely(value == 0))
>       ^
> arch/x86/kernel/ptrace.c:206:2: note: here
>   default:
>   ^~~~~~~
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

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

-Kees

> ---
>  arch/x86/kernel/ptrace.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
> index 0fdbe89d0754..3c5bbe8e4120 100644
> --- a/arch/x86/kernel/ptrace.c
> +++ b/arch/x86/kernel/ptrace.c
> @@ -201,6 +201,7 @@ static int set_segment_reg(struct task_struct *task,
>  	case offsetof(struct user_regs_struct, ss):
>  		if (unlikely(value == 0))
>  			return -EIO;
> +		/* Else, fall through */
>  
>  	default:
>  		*pt_regs_access(task_pt_regs(task), offset) = value;
> -- 
> 2.22.0
> 

-- 
Kees Cook