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    Subject[PATCH 4.19 066/139] KVM: x86: Fix kernel info-leak in KVM_HC_CLOCK_PAIRING hypercall
    Date
    4.19-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Liran Alon <liran.alon@oracle.com>

    commit bcbfbd8ec21096027f1ee13ce6c185e8175166f6 upstream.

    kvm_pv_clock_pairing() allocates local var
    "struct kvm_clock_pairing clock_pairing" on stack and initializes
    all it's fields besides padding (clock_pairing.pad[]).

    Because clock_pairing var is written completely (including padding)
    to guest memory, failure to init struct padding results in kernel
    info-leak.

    Fix the issue by making sure to also init the padding with zeroes.

    Fixes: 55dd00a73a51 ("KVM: x86: add KVM_HC_CLOCK_PAIRING hypercall")
    Reported-by: syzbot+a8ef68d71211ba264f56@syzkaller.appspotmail.com
    Reviewed-by: Mark Kanda <mark.kanda@oracle.com>
    Signed-off-by: Liran Alon <liran.alon@oracle.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/kvm/x86.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -6788,6 +6788,7 @@ static int kvm_pv_clock_pairing(struct k
    clock_pairing.nsec = ts.tv_nsec;
    clock_pairing.tsc = kvm_read_l1_tsc(vcpu, cycle);
    clock_pairing.flags = 0;
    + memset(&clock_pairing.pad, 0, sizeof(clock_pairing.pad));

    ret = 0;
    if (kvm_write_guest(vcpu->kvm, paddr, &clock_pairing,

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