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KVM: x86: Catch potential overrun in MCE setup

PATCH Applied Jan Kiszka 2 participants 2 messages Oct 23, 2009

Subsystems (3)
x86 KVM KVM x86
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Jan Kiszka

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#0 lore raw

PATCH 1/1 KVM: x86: Catch potential overrun in MCE setup

We only allocate memory for 32 MCE banks (KVM_MAX_MCE_BANKS) but we allow user space to fill up to 255 on setup (mcg_cap & 0xff), corrupting kernel memory. Catch these overflows.

Signed-off-by Jan Kiszka <[email protected]>

---

 arch/x86/kvm/x86.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
arch/x86/kvm/x86.c +1 -1
index c1e9094..e2fb5e0 100644
@@ -1720,7 +1720,7 @@ static int kvm_vcpu_ioctl_x86_setup_mce(struct kvm_vcpu *vcpu,
 	unsigned bank_num = mcg_cap & 0xff, bank;
 
 	r = -EINVAL;
-	if (!bank_num)
+	if (!bank_num || bank_num >= KVM_MAX_MCE_BANKS)
 		goto out;
 	if (mcg_cap & ~(KVM_MCE_CAP_SUPPORTED | 0xff | 0xff0000))
 		goto out;
Applied
#1 lore raw
Quoted 5 lines · Jan Kiszka

We only allocate memory for 32 MCE banks (KVM_MAX_MCE_BANKS) but we allow user space to fill up to 255 on setup (mcg_cap & 0xff), corrupting kernel memory. Catch these overflows.

Signed-off-by Jan Kiszka <[email protected]>

Applied, thanks.