linux-kernel - [PATCH 5/5] KVM: x86: Bail to userspace if emulation of atomic user access faults

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: <20220201010838.1494405-6-seanjc@google.com>
Date:   Tue,  1 Feb 2022 01:08:38 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        llvm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        syzbot+6cde2282daa792c49ab8@...kaller.appspotmail.com
Subject: [PATCH 5/5] KVM: x86: Bail to userspace if emulation of atomic user
 access faults

Exit to userspace when emulating an atomic guest access if the CMPXCHG on
the userspace address faults.  Emulating the access as a write and thus
likely treating it as emulated MMIO is wrong, as KVM has already
confirmed there is a valid, writable memslot.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/x86.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 37064d565bbc..66c5410dd4c3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7217,7 +7217,7 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
 	}
 
 	if (r < 0)
-		goto emul_write;
+		return X86EMUL_UNHANDLEABLE;
 	if (r)
 		return X86EMUL_CMPXCHG_FAILED;
 
-- 
2.35.0.rc2.247.g8bbb082509-goog