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    Subject[PATCH 5.14 049/172] ptp: Fix ptp_kvm_getcrosststamp issue for x86 ptp_kvm
    Date
    From: Zelin Deng <zelin.deng@linux.alibaba.com>

    commit 773e89ab0056aaa2baa1ffd9f044551654410104 upstream.

    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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/ptp/ptp_kvm_x86.c | 9 ++-------
    1 file changed, 2 insertions(+), 7 deletions(-)

    --- 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 *cy
    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 {
    /*

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