Re: [REGRESSION] x86/entry: Tracer no longer has opportunity to change the syscall number at entry via orig_ax

[Michael Ellerman]

Kees Cook <keescook@xxxxxxxxxxxx> writes:
> On Sun, Sep 13, 2020 at 08:27:23PM +0200, Thomas Gleixner wrote:
>> On Sun, Sep 13 2020 at 17:44, Michael Ellerman wrote:
>> > Kees Cook <keescook@xxxxxxxxxxxx> writes:
>> > diff --git a/kernel/entry/common.c b/kernel/entry/common.c
>> > index 18683598edbc..901361e2f8ea 100644
>> > --- a/kernel/entry/common.c
>> > +++ b/kernel/entry/common.c
>> > @@ -60,13 +60,15 @@ static long syscall_trace_enter(struct pt_regs *regs, long syscall,
>> >                         return ret;
>> >         }
>> >  
>> > +       syscall = syscall_get_nr(current, regs);
>> > +
>> >         if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT))
>> >                 trace_sys_enter(regs, syscall);
>> >  
>> >         syscall_enter_audit(regs, syscall);
>> >  
>> >         /* The above might have changed the syscall number */
>> > -       return ret ? : syscall_get_nr(current, regs);
>> > +       return ret ? : syscall;
>> >  }
>> 
>> Yup, this looks right. Can you please send a proper patch?
>
> I already did on Friday:
> https://lore.kernel.org/lkml/20200912005826.586171-1-keescook@xxxxxxxxxxxx/

Thanks.

cheers