Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Kees Cook <keescook@chromium.org>,
        Thomas Gleixner <tglx@linutronix.de>
Cc:     Robert O'Callahan <rocallahan@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "maintainer\:X86 ARCHITECTURE \(32-BIT AND 64-BIT\)" <x86@kernel.org>,
        linux-arch@vger.kernel.org, Will Deacon <will@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Mark Rutland <mark.rutland@arm.com>,
        Keno Fischer <keno@juliacomputing.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        kvm list <kvm@vger.kernel.org>,
        Gabriel Krisman Bertazi <krisman@collabora.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Kyle Huey <me@kylehuey.com>
Subject: Re: [REGRESSION] x86/entry: Tracer no longer has opportunity to change the syscall number at entry via orig_ax
In-Reply-To: <202009141303.08B39E5783@keescook>
References: <CAP045Arc1Vdh+n2j2ELE3q7XfagLjyqXji9ZD0jqwVB-yuzq-g@mail.gmail.com> <87blj6ifo8.fsf@nanos.tec.linutronix.de> <87a6xzrr89.fsf@mpe.ellerman.id.au> <202009111609.61E7875B3@keescook> <87d02qqfxy.fsf@mpe.ellerman.id.au> <87o8m98rck.fsf@nanos.tec.linutronix.de> <202009141303.08B39E5783@keescook>
Date:   Thu, 17 Sep 2020 10:39:40 +1000
Message-ID: <875z8dp777.fsf@mpe.ellerman.id.au>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Kees Cook <keescook@chromium.org> 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@chromium.org> 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@chromium.org/

Thanks.

cheers