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* fix for module unload vs. deferred jump labels (note: there might be

Browse source 
other buggy modules!)
 * two NULL pointer dereferences from syzkaller
 * CVE from syzkaller, very serious on 4.10-rc, "just" kernel memory
   leak on releases
 * CVE from security@kernel.org, somewhat serious on AMD, less so on
   Intel
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull KVM fixes from Paolo Bonzini:

 - fix for module unload vs deferred jump labels (note: there might be
   other buggy modules!)

 - two NULL pointer dereferences from syzkaller

 - also syzkaller: fix emulation of fxsave/fxrstor/sgdt/sidt, problem
   made worse during this merge window, "just" kernel memory leak on
   releases

 - fix emulation of "mov ss" - somewhat serious on AMD, less so on Intel

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: x86: fix emulation of "MOV SS, null selector"
  KVM: x86: fix NULL deref in vcpu_scan_ioapic
  KVM: eventfd: fix NULL deref irqbypass consumer
  KVM: x86: Introduce segmented_write_std
  KVM: x86: flush pending lapic jump label updates on module unload
  jump_labels: API for flushing deferred jump label updates
This commit is contained in:
Linus Torvalds 2017-01-13 17:06:24 -08:00
commit 406732c932
7 changed files with 80 additions and 16 deletions
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68
arch/x86/kvm/emulate.c
View file

@ -818,6 +818,20 @@ static int segmented_read_std(struct x86_emulate_ctxt *ctxt,
return ctxt->ops->read_std(ctxt, linear, data, size, &ctxt->exception);
}
static int segmented_write_std(struct x86_emulate_ctxt *ctxt,
struct segmented_address addr,
void *data,
unsigned int size)
{
int rc;
ulong linear;
rc = linearize(ctxt, addr, size, true, &linear);
if (rc != X86EMUL_CONTINUE)
return rc;
return ctxt->ops->write_std(ctxt, linear, data, size, &ctxt->exception);
}
/*
* Prefetch the remaining bytes of the instruction without crossing page
* boundary if they are not in fetch_cache yet.
@ -1571,7 +1585,6 @@ static int write_segment_descriptor(struct x86_emulate_ctxt *ctxt,
&ctxt->exception);
}
/* Does not support long mode */
static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
u16 selector, int seg, u8 cpl,
enum x86_transfer_type transfer,
@ -1608,20 +1621,34 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
rpl = selector & 3;
/* NULL selector is not valid for TR, CS and SS (except for long mode) */
if ((seg == VCPU_SREG_CS
|| (seg == VCPU_SREG_SS
&& (ctxt->mode != X86EMUL_MODE_PROT64 || rpl != cpl))
|| seg == VCPU_SREG_TR)
&& null_selector)
goto exception;
/* TR should be in GDT only */
if (seg == VCPU_SREG_TR && (selector & (1 << 2)))
goto exception;
if (null_selector) /* for NULL selector skip all following checks */
/* NULL selector is not valid for TR, CS and (except for long mode) SS */
if (null_selector) {
if (seg == VCPU_SREG_CS || seg == VCPU_SREG_TR)
goto exception;
if (seg == VCPU_SREG_SS) {
if (ctxt->mode != X86EMUL_MODE_PROT64 || rpl != cpl)
goto exception;
/*
* ctxt->ops->set_segment expects the CPL to be in
* SS.DPL, so fake an expand-up 32-bit data segment.
*/
seg_desc.type = 3;
seg_desc.p = 1;
seg_desc.s = 1;
seg_desc.dpl = cpl;
seg_desc.d = 1;
seg_desc.g = 1;
}
/* Skip all following checks */
goto load;
}
ret = read_segment_descriptor(ctxt, selector, &seg_desc, &desc_addr);
if (ret != X86EMUL_CONTINUE)
@ -1737,6 +1764,21 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
u16 selector, int seg)
{
u8 cpl = ctxt->ops->cpl(ctxt);
/*
* None of MOV, POP and LSS can load a NULL selector in CPL=3, but
* they can load it at CPL<3 (Intel's manual says only LSS can,
* but it's wrong).
*
* However, the Intel manual says that putting IST=1/DPL=3 in
* an interrupt gate will result in SS=3 (the AMD manual instead
* says it doesn't), so allow SS=3 in __load_segment_descriptor
* and only forbid it here.
*/
if (seg == VCPU_SREG_SS && selector == 3 &&
ctxt->mode == X86EMUL_MODE_PROT64)
return emulate_exception(ctxt, GP_VECTOR, 0, true);
return __load_segment_descriptor(ctxt, selector, seg, cpl,
X86_TRANSFER_NONE, NULL);
}
@ -3685,7 +3727,7 @@ static int emulate_store_desc_ptr(struct x86_emulate_ctxt *ctxt,
}
/* Disable writeback. */
ctxt->dst.type = OP_NONE;
return segmented_write(ctxt, ctxt->dst.addr.mem,
return segmented_write_std(ctxt, ctxt->dst.addr.mem,
&desc_ptr, 2 + ctxt->op_bytes);
}
@ -3932,7 +3974,7 @@ static int em_fxsave(struct x86_emulate_ctxt *ctxt)
else
size = offsetof(struct fxregs_state, xmm_space[0]);
return segmented_write(ctxt, ctxt->memop.addr.mem, &fx_state, size);
return segmented_write_std(ctxt, ctxt->memop.addr.mem, &fx_state, size);
}
static int fxrstor_fixup(struct x86_emulate_ctxt *ctxt,
@ -3974,7 +4016,7 @@ static int em_fxrstor(struct x86_emulate_ctxt *ctxt)
if (rc != X86EMUL_CONTINUE)
return rc;
rc = segmented_read(ctxt, ctxt->memop.addr.mem, &fx_state, 512);
rc = segmented_read_std(ctxt, ctxt->memop.addr.mem, &fx_state, 512);
if (rc != X86EMUL_CONTINUE)
return rc;

6
arch/x86/kvm/lapic.c
View file

@ -2426,3 +2426,9 @@ void kvm_lapic_init(void)
jump_label_rate_limit(&apic_hw_disabled, HZ);
jump_label_rate_limit(&apic_sw_disabled, HZ);
}
void kvm_lapic_exit(void)
{
static_key_deferred_flush(&apic_hw_disabled);
static_key_deferred_flush(&apic_sw_disabled);
}

1
arch/x86/kvm/lapic.h
View file

@ -110,6 +110,7 @@ static inline bool kvm_hv_vapic_assist_page_enabled(struct kvm_vcpu *vcpu)
int kvm_lapic_enable_pv_eoi(struct kvm_vcpu *vcpu, u64 data);
void kvm_lapic_init(void);
void kvm_lapic_exit(void);
#define VEC_POS(v) ((v) & (32 - 1))
#define REG_POS(v) (((v) >> 5) << 4)

3
arch/x86/kvm/x86.c
View file

@ -3342,6 +3342,8 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
switch (cap->cap) {
case KVM_CAP_HYPERV_SYNIC:
if (!irqchip_in_kernel(vcpu->kvm))
return -EINVAL;
return kvm_hv_activate_synic(vcpu);
default:
return -EINVAL;
@ -6045,6 +6047,7 @@ int kvm_arch_init(void *opaque)
void kvm_arch_exit(void)
{
kvm_lapic_exit();
perf_unregister_guest_info_callbacks(&kvm_guest_cbs);
if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC))

5
include/linux/jump_label_ratelimit.h
View file

@ -14,6 +14,7 @@ struct static_key_deferred {
#ifdef HAVE_JUMP_LABEL
extern void static_key_slow_dec_deferred(struct static_key_deferred *key);
extern void static_key_deferred_flush(struct static_key_deferred *key);
extern void
jump_label_rate_limit(struct static_key_deferred *key, unsigned long rl);
@ -26,6 +27,10 @@ static inline void static_key_slow_dec_deferred(struct static_key_deferred *key)
STATIC_KEY_CHECK_USE();
static_key_slow_dec(&key->key);
}
static inline void static_key_deferred_flush(struct static_key_deferred *key)
{
STATIC_KEY_CHECK_USE();
}
static inline void
jump_label_rate_limit(struct static_key_deferred *key,
unsigned long rl)

7
kernel/jump_label.c
View file

@ -182,6 +182,13 @@ void static_key_slow_dec_deferred(struct static_key_deferred *key)
}
EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);
void static_key_deferred_flush(struct static_key_deferred *key)
{
STATIC_KEY_CHECK_USE();
flush_delayed_work(&key->work);
}
EXPORT_SYMBOL_GPL(static_key_deferred_flush);
void jump_label_rate_limit(struct static_key_deferred *key,
unsigned long rl)
{

4
virt/lib/irqbypass.c
View file

@ -195,7 +195,7 @@ int irq_bypass_register_consumer(struct irq_bypass_consumer *consumer)
mutex_lock(&lock);
list_for_each_entry(tmp, &consumers, node) {
if (tmp->token == consumer->token) {
if (tmp->token == consumer->token || tmp == consumer) {
mutex_unlock(&lock);
module_put(THIS_MODULE);
return -EBUSY;
@ -245,7 +245,7 @@ void irq_bypass_unregister_consumer(struct irq_bypass_consumer *consumer)
mutex_lock(&lock);
list_for_each_entry(tmp, &consumers, node) {
if (tmp->token != consumer->token)
if (tmp != consumer)
continue;
list_for_each_entry(producer, &producers, node) {