From: Liran Alon Date: Thu, 8 Nov 2018 00:43:06 +0200 Subject: KVM: x86: Fix kernel info-leak in KVM_HC_CLOCK_PAIRING hypercall Git-commit: bcbfbd8ec21096027f1ee13ce6c185e8175166f6 Patch-mainline: v4.20-rc5 References: bsc#1106240 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 Signed-off-by: Liran Alon Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini Acked-by: Joerg Roedel --- arch/x86/kvm/x86.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 64cae03b2c20..7e4be1f2f253 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6918,6 +6918,7 @@ static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr, 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,