linux-kernel - Re: [PATCH 1/4] arm64: expose orig_x0 in the user_pt

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CANaxB-xTrMkJ2D19wwjSbCfizdRDnNO52fibpaRXP5g3hOcQwQ@mail.gmail.com>
Date:   Fri, 26 Mar 2021 17:35:19 -0700
From:   Andrei Vagin <avagin@...il.com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Will Deacon <will@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
        linux-arm-kernel@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        Dave Martin <Dave.Martin@....com>,
        Keno Fischer <keno@...iacomputing.com>
Subject: Re: [PATCH 1/4] arm64: expose orig_x0 in the user_pt_regs structure

On Fri, Mar 26, 2021 at 11:28 AM Catalin Marinas
<catalin.marinas@....com> wrote:
>
> On Mon, Mar 22, 2021 at 03:50:50PM -0700, Andrei Vagin wrote:
> > diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h
> > index 758ae984ff97..3c118c5b0893 100644
> > --- a/arch/arm64/include/uapi/asm/ptrace.h
> > +++ b/arch/arm64/include/uapi/asm/ptrace.h
> > @@ -90,6 +90,7 @@ struct user_pt_regs {
> >       __u64           sp;
> >       __u64           pc;
> >       __u64           pstate;
> > +     __u64           orig_x0;
> >  };
>
> That's a UAPI change, likely to go wrong. For example, a
> ptrace(PTRACE_GETREGSET, pid, REGSET_GPR, data) would write past the end
> of an old struct user_pt_regs in the debugger.

ptrace(PTRACE_GETREGSET, ...) receives iovec:
ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov)

iov contains a pointer to a buffer and its size and the kernel fills
only the part that fits the buffer.
I think this interface was invented to allow extending structures
without breaking backward compatibility.

>
> --
> Catalin