linux-kernel - Re: [RFC][PATCH 01/22] x86 user stack frame reads: switch to explicit __get

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Message-ID: <20200324151500.GQ20696@hirez.programming.kicks-ass.net>
Date:   Tue, 24 Mar 2020 16:15:00 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 01/22] x86 user stack frame reads: switch to
 explicit __get_user()

On Mon, Mar 23, 2020 at 06:37:58PM +0000, Al Viro wrote:
> From: Al Viro <viro@...iv.linux.org.uk>
> 
> rather than relying upon the magic in raw_copy_from_user()
> 
> Signed-off-by: Al Viro <viro@...iv.linux.org.uk>


> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
> index 61d93f062a36..ab8eab43a8a2 100644
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -695,15 +695,6 @@ extern struct movsl_mask {
>  #endif
>  
>  /*
> - * We rely on the nested NMI work to allow atomic faults from the NMI path; the
> - * nested NMI paths are careful to preserve CR2.
> - *
> - * Caller must use pagefault_enable/disable, or run in interrupt context,
> - * and also do a uaccess_ok() check
> - */
> -#define __copy_from_user_nmi __copy_from_user_inatomic
> -
> -/*
>   * The "unsafe" user accesses aren't really "unsafe", but the naming
>   * is a big fat warning: you have to not only do the access_ok()
>   * checking before using them, but you have to surround them with the

Thanks for killing that remnant!

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>