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 <[email protected]>
> Cc: Dave Hansen <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Alexei Starovoitov <[email protected]>
> Cc: Daniel Borkmann <[email protected]>
> Signed-off-by: Andy Lutomirski <[email protected]>
> ---
> 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.
https://people.kernel.org/tglx/notes-about-netiquette
