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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Zhiyi Guo <zhguo@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sasha Levin <sashal@kernel.org>,
	"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
	Laszlo Ersek <lersek@redhat.com>
Subject: [PATCH 4.19 09/29] KVM: SVM: relax conditions for allowing MSR_IA32_SPEC_CTRL accesses
Date: Tue,  5 Jan 2021 10:28:55 +0100	[thread overview]
Message-ID: <20210105090819.728680989@linuxfoundation.org> (raw)
In-Reply-To: <20210105090818.518271884@linuxfoundation.org>

From: Paolo Bonzini <pbonzini@redhat.com>

[ Upstream commit df7e8818926eb4712b67421442acf7d568fe2645 ]

Userspace that does not know about the AMD_IBRS bit might still
allow the guest to protect itself with MSR_IA32_SPEC_CTRL using
the Intel SPEC_CTRL bit.  However, svm.c disallows this and will
cause a #GP in the guest when writing to the MSR.  Fix this by
loosening the test and allowing the Intel CPUID bit, and in fact
allow the AMD_STIBP bit as well since it allows writing to
MSR_IA32_SPEC_CTRL too.

Reported-by: Zhiyi Guo <zhguo@redhat.com>
Analyzed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Analyzed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kvm/svm.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index a0c3d1b4b295b..f513110983d4c 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4209,6 +4209,8 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		break;
 	case MSR_IA32_SPEC_CTRL:
 		if (!msr_info->host_initiated &&
+		    !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL) &&
+		    !guest_cpuid_has(vcpu, X86_FEATURE_AMD_STIBP) &&
 		    !guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS) &&
 		    !guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD))
 			return 1;
@@ -4312,6 +4314,8 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 		break;
 	case MSR_IA32_SPEC_CTRL:
 		if (!msr->host_initiated &&
+		    !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL) &&
+		    !guest_cpuid_has(vcpu, X86_FEATURE_AMD_STIBP) &&
 		    !guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS) &&
 		    !guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD))
 			return 1;
-- 
2.27.0




  parent reply	other threads:[~2021-01-05  9:30 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-05  9:28 [PATCH 4.19 00/29] 4.19.165-rc2 review Greg Kroah-Hartman
2021-01-05  9:28 ` [PATCH 4.19 01/29] md/raid10: initialize r10_bio->read_slot before use Greg Kroah-Hartman
2021-01-05  9:28 ` [PATCH 4.19 02/29] fscrypt: add fscrypt_is_nokey_name() Greg Kroah-Hartman
2021-01-05  9:28 ` [PATCH 4.19 03/29] ext4: prevent creating duplicate encrypted filenames Greg Kroah-Hartman
2021-01-05  9:28 ` [PATCH 4.19 04/29] f2fs: " Greg Kroah-Hartman
2021-01-05  9:28 ` [PATCH 4.19 05/29] ubifs: " Greg Kroah-Hartman
2021-01-05  9:28 ` [PATCH 4.19 06/29] vfio/pci: Move dummy_resources_list init in vfio_pci_probe() Greg Kroah-Hartman
2021-01-05  9:28 ` [PATCH 4.19 07/29] ext4: dont remount read-only with errors=continue on reboot Greg Kroah-Hartman
2021-01-05  9:28 ` [PATCH 4.19 08/29] uapi: move constants from <linux/kernel.h> to <linux/const.h> Greg Kroah-Hartman
2021-01-05  9:28 ` Greg Kroah-Hartman [this message]
2021-01-05  9:28 ` [PATCH 4.19 10/29] KVM: x86: reinstate vendor-agnostic check on SPEC_CTRL cpuid bits Greg Kroah-Hartman
2021-01-05  9:28 ` [PATCH 4.19 11/29] powerpc/bitops: Fix possible undefined behaviour with fls() and fls64() Greg Kroah-Hartman
2021-01-05  9:28 ` [PATCH 4.19 12/29] xen/gntdev.c: Mark pages as dirty Greg Kroah-Hartman
2021-01-05  9:28 ` [PATCH 4.19 13/29] null_blk: Fix zone size initialization Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 14/29] of: fix linker-section match-table corruption Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 15/29] Bluetooth: hci_h5: close serdev device and free hu in h5_close Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 16/29] reiserfs: add check for an invalid ih_entry_count Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 17/29] misc: vmw_vmci: fix kernel info-leak by initializing dbells in vmci_ctx_get_chkpt_doorbells() Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 18/29] media: gp8psk: initialize stats at power control logic Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 19/29] ALSA: seq: Use bool for snd_seq_queue internal flags Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 20/29] ALSA: rawmidi: Access runtime->avail always in spinlock Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 21/29] fcntl: Fix potential deadlock in send_sig{io, urg}() Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 22/29] rtc: sun6i: Fix memleak in sun6i_rtc_clk_init Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 23/29] module: set MODULE_STATE_GOING state when a module fails to load Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 24/29] quota: Dont overflow quota file offsets Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 25/29] powerpc: sysdev: add missing iounmap() on error in mpic_msgr_probe() Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 26/29] NFSv4: Fix a pNFS layout related use-after-free race when freeing the inode Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 27/29] module: delay kobject uevent until after module init call Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 28/29] ALSA: pcm: Clear the full allocated memory at hw_params Greg Kroah-Hartman
2021-01-05  9:29 ` [PATCH 4.19 29/29] dm verity: skip verity work if I/O error when system is shutting down Greg Kroah-Hartman
2021-01-05 10:12 ` [PATCH 4.19 00/29] 4.19.165-rc2 review Pavel Machek
2021-01-06 13:46   ` Greg Kroah-Hartman
2021-01-05 11:08 ` Jon Hunter
2021-01-06 13:46   ` Greg Kroah-Hartman
2021-01-05 18:16 ` Guenter Roeck
2021-01-06 13:45   ` Greg Kroah-Hartman
2021-01-05 22:29 ` Daniel Díaz
2021-01-06 13:45   ` Greg Kroah-Hartman

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