From: Paolo Bonzini <pbonzini@redhat.com>
To: Nick Desaulniers <ndesaulniers@google.com>,
Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.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 20:39:58 +0100 [thread overview]
Message-ID: <887add8e-cc74-b50b-46f8-f51d39c12dff@redhat.com> (raw)
In-Reply-To: <CAKwvOdnwhoHe8ouao2VBo1meRd8H4EOC7Nr8hnFkbXBACWRm9w@mail.gmail.com>
On 23/03/20 20:30, Nick Desaulniers wrote:
> <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.
Yes, this is fair enough. I've queued your patch and will send it
shortly to Linus.
Paolo
next prev parent reply other threads:[~2020-03-23 19:40 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 ` BUG: unable to handle kernel NULL pointer dereference in handle_external_interrupt_irqoff Nick Desaulniers
2020-03-23 19:39 ` Paolo Bonzini [this message]
2020-03-22 8:53 ` syzbot
2020-03-22 13:29 ` syzbot
2020-03-22 13:43 ` Dmitry Vyukov
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