linux-kernel - Re: [PATCH v4 07/10] x86: narrow out of bounds syscalls to sys

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Date:   Wed, 24 Jan 2018 15:40:40 +0100
From:   Jiri Slaby <jslaby@...e.cz>
To:     Dan Williams <dan.j.williams@...el.com>,
        linux-kernel@...r.kernel.org
Cc:     linux-arch@...r.kernel.org, kernel-hardening@...ts.openwall.com,
        gregkh@...uxfoundation.org, x86@...nel.org,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, tglx@...utronix.de,
        torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
        alan@...ux.intel.com
Subject: Re: [PATCH v4 07/10] x86: narrow out of bounds syscalls to sys_read
 under speculation

On 01/19/2018, 01:02 AM, Dan Williams wrote:
> The syscall table base is a user controlled function pointer in kernel
> space. Like, 'get_user, use 'MASK_NOSPEC' to prevent any out of bounds
> speculation. While retpoline prevents speculating into the user
> controlled target it does not stop the pointer de-reference, the concern
> is leaking memory relative to the syscall table base.
> 
> Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: x86@...nel.org
> Cc: Andy Lutomirski <luto@...nel.org>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
>  arch/x86/entry/entry_64.S   |    2 ++
>  arch/x86/include/asm/smap.h |    9 ++++++++-
>  2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
> index 4f8e1d35a97c..2320017077d4 100644
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -35,6 +35,7 @@
>  #include <asm/asm.h>
>  #include <asm/smap.h>
>  #include <asm/pgtable_types.h>
> +#include <asm/smap.h>

This is already included 2 lines above

thanks,
-- 
js
suse labs