From: Nick Desaulniers <ndesaulniers@google.com>
To: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
syzbot <syzbot+3f29ca2efb056a761e38@syzkaller.appspotmail.com>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
KVM list <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
Thomas Gleixner <tglx@linutronix.de>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
"the arch/x86 maintainers" <x86@kernel.org>,
Sean Christopherson <sean.j.christopherson@intel.com>
Subject: Re: BUG: unable to handle kernel NULL pointer dereference in handle_external_interrupt_irqoff
Date: Mon, 23 Mar 2020 12:30:53 -0700 [thread overview]
Message-ID: <CAKwvOdnwhoHe8ouao2VBo1meRd8H4EOC7Nr8hnFkbXBACWRm9w@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdn10Ts_AU6i+7toj7NkMwK-+0yr5wTrN0XEDudBWS0sPQ@mail.gmail.com>
On Mon, Mar 23, 2020 at 11:49 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> So maybe we can find why
> commit 76b043848fd2 ("x86/retpoline: Add initial retpoline support")
> added THUNK_TARGET with and without "m" constraint, and either:
> - remove "m" from THUNK_TARGET. (Maybe this doesn't compile somewhere)
> or
> - use my above recommendation locally avoiding THUNK_TARGET. We can
> use "r" rather than "a" (what Clang would have picked) or "b (what GCC
> would have picked) to give the compilers maximal flexibility.
So I've sent a patch for the latter; my reason for not pursuing the former is:
1. I assume that the thunk target could be spilled, or a pointer, and
we'd like to keep flexibility for the general case of inline asm that
doesn't modify the stack pointer.
2. `entry` is local to `handle_external_interrupt_irqoff`; it's not
being passed in via pointer as a function parameter.
3. register pressure is irrelevant if the resulting code is incorrect.
--
Thanks,
~Nick Desaulniers
next prev parent reply other threads:[~2020-03-23 19:31 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-22 6:43 BUG: unable to handle kernel NULL pointer dereference in handle_external_interrupt_irqoff syzbot
2020-03-22 6:59 ` Dmitry Vyukov
2020-03-22 7:03 ` Dmitry Vyukov
2020-03-23 8:18 ` Paolo Bonzini
2020-03-23 16:31 ` Alexander Potapenko
2020-03-23 16:39 ` Sean Christopherson
2020-03-23 16:43 ` Alexander Potapenko
2020-03-23 16:57 ` Nick Desaulniers
2020-03-23 17:28 ` Nick Desaulniers
2020-03-23 17:55 ` Alexander Potapenko
2020-03-23 18:06 ` Nick Desaulniers
2020-03-23 18:06 ` Alexander Potapenko
2020-03-23 18:16 ` Nick Desaulniers
2020-03-23 18:49 ` Nick Desaulniers
2020-03-23 19:12 ` [PATCH] KVM: VMX: don't allow memory operands for inline asm that modifies SP Nick Desaulniers
2020-03-23 19:30 ` Nick Desaulniers [this message]
2020-03-23 19:39 ` BUG: unable to handle kernel NULL pointer dereference in handle_external_interrupt_irqoff Paolo Bonzini
2020-03-22 8:53 ` syzbot
2020-03-22 13:29 ` syzbot
2020-03-22 13:43 ` Dmitry Vyukov
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