linux-kernel - [PATCH v2 0/2] Relax canonical checks on some arch msrs

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-next>] [day] [month] [year] [list]

Message-Id: <20240802151608.72896-1-mlevitsk@redhat.com>
Date: Fri,  2 Aug 2024 18:16:06 +0300
From: Maxim Levitsky <mlevitsk@...hat.com>
To: kvm@...r.kernel.org
Cc: Sean Christopherson <seanjc@...gle.com>,
	linux-kernel@...r.kernel.org,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	x86@...nel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH v2 0/2] Relax canonical checks on some arch msrs

Recently we came up upon a failure where likely the guest writes
0xff4547ceb1600000 to MSR_KERNEL_GS_BASE and later on, qemu
sets this value via KVM_PUT_MSRS, and is rejected by the
kernel, likely due to not being canonical in 4 level paging.

I did some reverse engineering and to my surprise I found out
that both Intel and AMD have very loose checks in regard to
non canonical addresses written to this and several other msrs,
when the CPU supports 5 level paging.

Patch #1 addresses this, making KVM tolerate this.

Patch #2 is just a fix for a semi theoretical bug, found
while trying to debug the issue.

V2: addressed a very good feedback from Chao Gao. Thanks!

Best regards,
	Maxim Levitsky

Maxim Levitsky (2):
  KVM: x86: relax canonical check for some x86 architectural msrs
  KVM: SVM: fix emulation of msr reads/writes of MSR_FS_BASE and
    MSR_GS_BASE

 arch/x86/kvm/svm/svm.c | 12 ++++++++++++
 arch/x86/kvm/x86.c     | 11 ++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

-- 
2.40.1