From: Nick Desaulniers <ndesaulniers@google.com>
To: pbonzini@redhat.com, sean.j.christopherson@intel.com
Cc: ndesaulniers@google.com, bp@alien8.de,
clang-built-linux@googlegroups.com, dvyukov@google.com,
glider@google.com, hpa@zytor.com, jmattson@google.com,
joro@8bytes.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, mingo@redhat.com,
syzbot+3f29ca2efb056a761e38@syzkaller.appspotmail.com,
syzkaller-bugs@googlegroups.com, tglx@linutronix.de,
vkuznets@redhat.com, wanpengli@tencent.com, x86@kernel.org
Subject: [PATCH] KVM: VMX: don't allow memory operands for inline asm that modifies SP
Date: Mon, 23 Mar 2020 12:12:43 -0700 [thread overview]
Message-ID: <20200323191243.30002-1-ndesaulniers@google.com> (raw)
In-Reply-To: <CAKwvOdn10Ts_AU6i+7toj7NkMwK-+0yr5wTrN0XEDudBWS0sPQ@mail.gmail.com>
THUNK_TARGET defines [thunk_target] as having "rm" input constraints
when CONFIG_RETPOLINE is not set, which isn't constrained enough for
this specific case.
For inline assembly that modifies the stack pointer before using this
input, the underspecification of constraints is dangerous, and results
in an indirect call to a previously pushed flags register.
In this case `entry`'s stack slot is good enough to satisfy the "m"
constraint in "rm", but the inline assembly in
handle_external_interrupt_irqoff() modifies the stack pointer via
push+pushf before using this input, which in this case results in
calling what was the previous state of the flags register, rather than
`entry`.
Be more specific in the constraints by requiring `entry` be in a
register, and not a memory operand.
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Reported-by: syzbot+3f29ca2efb056a761e38@syzkaller.appspotmail.com
Debugged-by: Alexander Potapenko <glider@google.com>
Debugged-by: Paolo Bonzini <pbonzini@redhat.com>
Debugged-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
arch/x86/kvm/vmx/vmx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4d22b1b5e822..310e8c1169b8 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6277,7 +6277,7 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
#endif
ASM_CALL_CONSTRAINT
:
- THUNK_TARGET(entry),
+ [thunk_target]"r"(entry),
[ss]"i"(__KERNEL_DS),
[cs]"i"(__KERNEL_CS)
);
--
2.25.1.696.g5e7596f4ac-goog
next prev parent reply other threads:[~2020-03-23 19:20 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 ` Nick Desaulniers [this message]
2020-03-23 19:30 ` Nick Desaulniers
2020-03-23 19:39 ` 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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