linux-kernel - [PATCH v2] KVM: kvmclock: Fix vCPUs

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]

Date:   Mon, 18 Jan 2021 17:07:53 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        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>,
        Brijesh Singh <brijesh.singh@....com>
Subject: [PATCH v2] KVM: kvmclock: Fix vCPUs > 64 can't be online/hotpluged

From: Wanpeng Li <wanpengli@...cent.com>

The per-cpu vsyscall pvclock data pointer assigns either an element of the 
static array hv_clock_boot (#vCPU <= 64) or dynamically allocated memory 
hvclock_mem (vCPU > 64), the dynamically memory will not be allocated if 
kvmclock vsyscall is disabled, this can result in cpu hotpluged fails in 
kvmclock_setup_percpu() which returns -ENOMEM. This patch fixes it by not 
assigning vsyscall pvclock data pointer if kvmclock vdso_clock_mode is not 
VDSO_CLOCKMODE_PVCLOCK.

Fixes: 6a1cac56f4 ("x86/kvm: Use __bss_decrypted attribute in shared variables")
Reported-by: Zelin Deng <zelin.deng@...ux.alibaba.com>
Tested-by: Haiwei Li <lihaiwei@...cent.com>
Cc: Brijesh Singh <brijesh.singh@....com>
Cc: stable@...r.kernel.org#v4.19-rc5+
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
v1 -> v2:
 * add code comments

 arch/x86/kernel/kvmclock.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index aa59374..01d4e55c 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -294,9 +294,11 @@ static int kvmclock_setup_percpu(unsigned int cpu)
 	/*
 	 * The per cpu area setup replicates CPU0 data to all cpu
 	 * pointers. So carefully check. CPU0 has been set up in init
-	 * already.
+	 * already. Assign vsyscall pvclock data pointer iff kvmclock
+	 * vsyscall is enabled.
 	 */
-	if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
+	if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)) ||
+	    (kvm_clock.vdso_clock_mode != VDSO_CLOCKMODE_PVCLOCK))
 		return 0;
 
 	/* Use the static page for the first CPUs, allocate otherwise */
-- 
2.7.4