From f8bb056564ed719b2fa5e05028bc70aeb0cc5c6c Mon Sep 17 00:00:00 2001 From: Igor Mammedov Date: Mon, 28 Jan 2013 12:49:26 +0100 Subject: [PATCH] target-i386: kvm: prevent buffer overflow if -cpu foo, [x]level is too big 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 Reviewed-by: Andreas Faerber Signed-off-by: Igor Mammedov Signed-off-by: Gleb Natapov --- 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 3acff40c47..4ecb728a5d 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; -- 2.11.0