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[Qemu-devel] [PATCH 2/2] target-i386: kvm: prevent buffer overflow if -c
From: |
Gleb Natapov |
Subject: |
[Qemu-devel] [PATCH 2/2] target-i386: kvm: prevent buffer overflow if -cpu foo, [x]level is too big |
Date: |
Tue, 29 Jan 2013 12:59:56 +0200 |
From: Igor Mammedov <address@hidden>
Stack corruption may occur if too big 'level' or 'xlevel' values passed
on command line with KVM enabled, due to limited size of cpuid_data
in kvm_arch_init_vcpu().
reproduces with:
qemu -enable-kvm -cpu qemu64,level=4294967295
or
qemu -enable-kvm -cpu qemu64,xlevel=4294967295
Check if there is space in cpuid_data before passing it to cpu_x86_cpuid()
or abort() if there is not space.
Reviewed-by: Laszlo Ersek <address@hidden>
Reviewed-by: Andreas Faerber <address@hidden>
Signed-off-by: Igor Mammedov <address@hidden>
Signed-off-by: Gleb Natapov <address@hidden>
---
target-i386/kvm.c | 25 ++++++++++++++++++++++++-
1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 3acff40..4ecb728 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -411,11 +411,12 @@ static void cpu_update_state(void *opaque, int running,
RunState state)
}
}
+#define KVM_MAX_CPUID_ENTRIES 100
int kvm_arch_init_vcpu(CPUState *cs)
{
struct {
struct kvm_cpuid2 cpuid;
- struct kvm_cpuid_entry2 entries[100];
+ struct kvm_cpuid_entry2 entries[KVM_MAX_CPUID_ENTRIES];
} QEMU_PACKED cpuid_data;
X86CPU *cpu = X86_CPU(cs);
CPUX86State *env = &cpu->env;
@@ -502,6 +503,10 @@ int kvm_arch_init_vcpu(CPUState *cs)
cpu_x86_cpuid(env, 0, 0, &limit, &unused, &unused, &unused);
for (i = 0; i <= limit; i++) {
+ if (cpuid_i == KVM_MAX_CPUID_ENTRIES) {
+ fprintf(stderr, "unsupported level value: 0x%x\n", limit);
+ abort();
+ }
c = &cpuid_data.entries[cpuid_i++];
switch (i) {
@@ -516,6 +521,11 @@ int kvm_arch_init_vcpu(CPUState *cs)
times = c->eax & 0xff;
for (j = 1; j < times; ++j) {
+ if (cpuid_i == KVM_MAX_CPUID_ENTRIES) {
+ fprintf(stderr, "cpuid_data is full, no space for "
+ "cpuid(eax:2):eax & 0xf = 0x%x\n", times);
+ abort();
+ }
c = &cpuid_data.entries[cpuid_i++];
c->function = i;
c->flags = KVM_CPUID_FLAG_STATEFUL_FUNC;
@@ -544,6 +554,11 @@ int kvm_arch_init_vcpu(CPUState *cs)
if (i == 0xd && c->eax == 0) {
continue;
}
+ if (cpuid_i == KVM_MAX_CPUID_ENTRIES) {
+ fprintf(stderr, "cpuid_data is full, no space for "
+ "cpuid(eax:0x%x,ecx:0x%x)\n", i, j);
+ abort();
+ }
c = &cpuid_data.entries[cpuid_i++];
}
break;
@@ -557,6 +572,10 @@ int kvm_arch_init_vcpu(CPUState *cs)
cpu_x86_cpuid(env, 0x80000000, 0, &limit, &unused, &unused, &unused);
for (i = 0x80000000; i <= limit; i++) {
+ if (cpuid_i == KVM_MAX_CPUID_ENTRIES) {
+ fprintf(stderr, "unsupported xlevel value: 0x%x\n", limit);
+ abort();
+ }
c = &cpuid_data.entries[cpuid_i++];
c->function = i;
@@ -569,6 +588,10 @@ int kvm_arch_init_vcpu(CPUState *cs)
cpu_x86_cpuid(env, 0xC0000000, 0, &limit, &unused, &unused, &unused);
for (i = 0xC0000000; i <= limit; i++) {
+ if (cpuid_i == KVM_MAX_CPUID_ENTRIES) {
+ fprintf(stderr, "unsupported xlevel2 value: 0x%x\n", limit);
+ abort();
+ }
c = &cpuid_data.entries[cpuid_i++];
c->function = i;
--
1.7.10.4