x86 software emulation (non-KVM mode) does not check privilege
levels on task gate switches ... so one can invoke a kernel's
double fault handler from user space.
Signed-off-by: Alex Zuepke <azu@sysgo.de>
@@ -578,12 +578,17 @@ static void do_interrupt_protected(CPUX86State *env, int intno, int is_int,
e2 = cpu_ldl_kernel(env, ptr + 4);
/* check gate type */
type = (e2 >> DESC_TYPE_SHIFT) & 0x1f;
+ dpl = (e2 >> DESC_DPL_SHIFT) & 3;
+ cpl = env->hflags & HF_CPL_MASK;
switch (type) {
case 5: /* task gate */
/* must do that check here to return the correct error code */
if (!(e2 & DESC_P_MASK)) {
raise_exception_err(env, EXCP0B_NOSEG, intno * 8 + 2);
}
+ /* check privilege if software int */
+ if (is_int && dpl < cpl)
+ raise_exception_err(env, EXCP0D_GPF, intno * 8 + 2);
switch_tss(env, intno * 8, e1, e2, SWITCH_TSS_CALL, old_eip);
if (has_error_code) {
int type;
@@ -616,8 +621,6 @@ static void do_interrupt_protected(CPUX86State *env, int intno, int is_int,
raise_exception_err(env, EXCP0D_GPF, intno * 8 + 2);
break;
}
- dpl = (e2 >> DESC_DPL_SHIFT) & 3;
- cpl = env->hflags & HF_CPL_MASK;
/* check privilege if software int */
if (is_int && dpl < cpl) {
raise_exception_err(env, EXCP0D_GPF, intno * 8 + 2);