The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 773e89ab0056aaa2baa1ffd9f044551654410104 Mon Sep 17 00:00:00 2001

From: Zelin Deng zelin.deng@linux.alibaba.com Date: Wed, 29 Sep 2021 13:13:49 +0800 Subject: [PATCH] ptp: Fix ptp_kvm_getcrosststamp issue for x86 ptp_kvm

hv_clock is preallocated to have only HVC_BOOT_ARRAY_SIZE (64) elements; if the PTP_SYS_OFFSET_PRECISE ioctl is executed on vCPUs whose index is 64 of higher, retrieving the struct pvclock_vcpu_time_info pointer with "src = &hv_clock[cpu].pvti" will result in an out-of-bounds access and a wild pointer. Change it to "this_cpu_pvti()" which is guaranteed to be valid.

Fixes: 95a3d4454bb1 ("Switch kvmclock data to a PER_CPU variable") Signed-off-by: Zelin Deng zelin.deng@linux.alibaba.com Cc: stable@vger.kernel.org Message-Id: 1632892429-101194-3-git-send-email-zelin.deng@linux.alibaba.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com

diff --git a/drivers/ptp/ptp_kvm_x86.c b/drivers/ptp/ptp_kvm_x86.c index 3dd519dfc473..d0096cd7096a 100644 --- a/drivers/ptp/ptp_kvm_x86.c +++ b/drivers/ptp/ptp_kvm_x86.c @@ -15,8 +15,6 @@ #include <linux/ptp_clock_kernel.h> #include <linux/ptp_kvm.h>

-struct pvclock_vsyscall_time_info *hv_clock; - static phys_addr_t clock_pair_gpa; static struct kvm_clock_pairing clock_pair;

@@ -28,8 +26,7 @@ int kvm_arch_ptp_init(void) return -ENODEV;

clock_pair_gpa = slow_virt_to_phys(&clock_pair); - hv_clock = pvclock_get_pvti_cpu0_va(); - if (!hv_clock) + if (!pvclock_get_pvti_cpu0_va()) return -ENODEV;

ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING, clock_pair_gpa, @@ -64,10 +61,8 @@ int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *tspec, struct pvclock_vcpu_time_info *src; unsigned int version; long ret; - int cpu;

- cpu = smp_processor_id(); - src = &hv_clock[cpu].pvti; + src = this_cpu_pvti();

do { /*