Re: [PATCH 10/11] x86/fault: Don't run fixups for SMAP violations

[Borislav Petkov]

On Sun, Jan 31, 2021 at 09:24:41AM -0800, Andy Lutomirski wrote:
> A SMAP-violating kernel access is not a recoverable condition.  Imagine
> kernel code that, outside of a uaccess region, dereferences a pointer to
> the user range by accident.  If SMAP is on, this will reliably generate
> as an intentional user access.  This makes it easy for bugs to be
> overlooked if code is inadequately tested both with and without SMAP.
> 
> We discovered this because BPF can generate invalid accesses to user
> memory, but those warnings only got printed if SMAP was off.  With this
> patch, this type of error will be discovered with SMAP on as well.
> 
> Cc: Yonghong Song <yhs@xxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
> ---
>  arch/x86/mm/fault.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 04cc98ec2423..d39946ad8a91 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -1242,7 +1242,11 @@ void do_user_addr_fault(struct pt_regs *regs,
>  		     !(error_code & X86_PF_USER) &&
>  		     !(regs->flags & X86_EFLAGS_AC)))
>  	{
	^

Might wanna fix that opening brace too.

-- 
Regards/Gruss,
    Boris.

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