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authorHuang Ying <ying.huang@intel.com>2010-05-31 14:28:19 +0800
committerAvi Kivity <avi@redhat.com>2010-08-01 10:35:26 +0300
commitbf998156d24bcb127318ad5bf531ac3bdfcd6449 (patch)
tree616c19474d7cb626ff9eebc54f6753563a4322cd
parent540ad6b62b3a188a53b51cac81d8a60d40e29fbd (diff)
KVM: Avoid killing userspace through guest SRAO MCE on unmapped pages
In common cases, guest SRAO MCE will cause corresponding poisoned page be un-mapped and SIGBUS be sent to QEMU-KVM, then QEMU-KVM will relay the MCE to guest OS. But it is reported that if the poisoned page is accessed in guest after unmapping and before MCE is relayed to guest OS, userspace will be killed. The reason is as follows. Because poisoned page has been un-mapped, guest access will cause guest exit and kvm_mmu_page_fault will be called. kvm_mmu_page_fault can not get the poisoned page for fault address, so kernel and user space MMIO processing is tried in turn. In user MMIO processing, poisoned page is accessed again, then userspace is killed by force_sig_info. To fix the bug, kvm_mmu_page_fault send HWPOISON signal to QEMU-KVM and do not try kernel and user space MMIO processing for poisoned page. [xiao: fix warning introduced by avi] Reported-by: Max Asbock <masbock@linux.vnet.ibm.com> Signed-off-by: Huang Ying <ying.huang@intel.com> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
-rw-r--r--arch/x86/kvm/mmu.c34
-rw-r--r--arch/x86/kvm/paging_tmpl.h7
-rw-r--r--include/linux/kvm_host.h1
-rw-r--r--include/linux/mm.h8
-rw-r--r--mm/memory-failure.c30
-rw-r--r--virt/kvm/kvm_main.c30
6 files changed, 95 insertions, 15 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index b1ed0a1a5913..b666d8d106a9 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -32,6 +32,7 @@
#include <linux/compiler.h>
#include <linux/srcu.h>
#include <linux/slab.h>
+#include <linux/uaccess.h>
#include <asm/page.h>
#include <asm/cmpxchg.h>
@@ -1960,6 +1961,27 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
return pt_write;
}
+static void kvm_send_hwpoison_signal(struct kvm *kvm, gfn_t gfn)
+{
+ char buf[1];
+ void __user *hva;
+ int r;
+
+ /* Touch the page, so send SIGBUS */
+ hva = (void __user *)gfn_to_hva(kvm, gfn);
+ r = copy_from_user(buf, hva, 1);
+}
+
+static int kvm_handle_bad_page(struct kvm *kvm, gfn_t gfn, pfn_t pfn)
+{
+ kvm_release_pfn_clean(pfn);
+ if (is_hwpoison_pfn(pfn)) {
+ kvm_send_hwpoison_signal(kvm, gfn);
+ return 0;
+ }
+ return 1;
+}
+
static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn)
{
int r;
@@ -1983,10 +2005,8 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn)
pfn = gfn_to_pfn(vcpu->kvm, gfn);
/* mmio */
- if (is_error_pfn(pfn)) {
- kvm_release_pfn_clean(pfn);
- return 1;
- }
+ if (is_error_pfn(pfn))
+ return kvm_handle_bad_page(vcpu->kvm, gfn, pfn);
spin_lock(&vcpu->kvm->mmu_lock);
if (mmu_notifier_retry(vcpu, mmu_seq))
@@ -2198,10 +2218,8 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa,
mmu_seq = vcpu->kvm->mmu_notifier_seq;
smp_rmb();
pfn = gfn_to_pfn(vcpu->kvm, gfn);
- if (is_error_pfn(pfn)) {
- kvm_release_pfn_clean(pfn);
- return 1;
- }
+ if (is_error_pfn(pfn))
+ return kvm_handle_bad_page(vcpu->kvm, gfn, pfn);
spin_lock(&vcpu->kvm->mmu_lock);
if (mmu_notifier_retry(vcpu, mmu_seq))
goto out_unlock;
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 2331bdc2b549..c7f27779c998 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -431,11 +431,8 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
pfn = gfn_to_pfn(vcpu->kvm, walker.gfn);
/* mmio */
- if (is_error_pfn(pfn)) {
- pgprintk("gfn %lx is mmio\n", walker.gfn);
- kvm_release_pfn_clean(pfn);
- return 1;
- }
+ if (is_error_pfn(pfn))
+ return kvm_handle_bad_page(vcpu->kvm, walker.gfn, pfn);
spin_lock(&vcpu->kvm->mmu_lock);
if (mmu_notifier_retry(vcpu, mmu_seq))
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7cb116afa1cd..a0e019769f5d 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -266,6 +266,7 @@ extern pfn_t bad_pfn;
int is_error_page(struct page *page);
int is_error_pfn(pfn_t pfn);
+int is_hwpoison_pfn(pfn_t pfn);
int kvm_is_error_hva(unsigned long addr);
int kvm_set_memory_region(struct kvm *kvm,
struct kvm_userspace_memory_region *mem,
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a2b48041b910..7a9ab7db1975 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1465,6 +1465,14 @@ extern int sysctl_memory_failure_recovery;
extern void shake_page(struct page *p, int access);
extern atomic_long_t mce_bad_pages;
extern int soft_offline_page(struct page *page, int flags);
+#ifdef CONFIG_MEMORY_FAILURE
+int is_hwpoison_address(unsigned long addr);
+#else
+static inline int is_hwpoison_address(unsigned long addr)
+{
+ return 0;
+}
+#endif
extern void dump_page(struct page *page);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 620b0b461593..378b0f61fd3c 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -45,6 +45,7 @@
#include <linux/page-isolation.h>
#include <linux/suspend.h>
#include <linux/slab.h>
+#include <linux/swapops.h>
#include "internal.h"
int sysctl_memory_failure_early_kill __read_mostly = 0;
@@ -1296,3 +1297,32 @@ done:
/* keep elevated page count for bad page */
return ret;
}
+
+int is_hwpoison_address(unsigned long addr)
+{
+ pgd_t *pgdp;
+ pud_t pud, *pudp;
+ pmd_t pmd, *pmdp;
+ pte_t pte, *ptep;
+ swp_entry_t entry;
+
+ pgdp = pgd_offset(current->mm, addr);
+ if (!pgd_present(*pgdp))
+ return 0;
+ pudp = pud_offset(pgdp, addr);
+ pud = *pudp;
+ if (!pud_present(pud) || pud_large(pud))
+ return 0;
+ pmdp = pmd_offset(pudp, addr);
+ pmd = *pmdp;
+ if (!pmd_present(pmd) || pmd_large(pmd))
+ return 0;
+ ptep = pte_offset_map(pmdp, addr);
+ pte = *ptep;
+ pte_unmap(ptep);
+ if (!is_swap_pte(pte))
+ return 0;
+ entry = pte_to_swp_entry(pte);
+ return is_hwpoison_entry(entry);
+}
+EXPORT_SYMBOL_GPL(is_hwpoison_address);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index f032806a212f..187aa8d984a7 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -92,6 +92,9 @@ static bool kvm_rebooting;
static bool largepages_enabled = true;
+struct page *hwpoison_page;
+pfn_t hwpoison_pfn;
+
inline int kvm_is_mmio_pfn(pfn_t pfn)
{
if (pfn_valid(pfn)) {
@@ -810,16 +813,22 @@ EXPORT_SYMBOL_GPL(kvm_disable_largepages);
int is_error_page(struct page *page)
{
- return page == bad_page;
+ return page == bad_page || page == hwpoison_page;
}
EXPORT_SYMBOL_GPL(is_error_page);
int is_error_pfn(pfn_t pfn)
{
- return pfn == bad_pfn;
+ return pfn == bad_pfn || pfn == hwpoison_pfn;
}
EXPORT_SYMBOL_GPL(is_error_pfn);
+int is_hwpoison_pfn(pfn_t pfn)
+{
+ return pfn == hwpoison_pfn;
+}
+EXPORT_SYMBOL_GPL(is_hwpoison_pfn);
+
static inline unsigned long bad_hva(void)
{
return PAGE_OFFSET;
@@ -945,6 +954,11 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr)
if (unlikely(npages != 1)) {
struct vm_area_struct *vma;
+ if (is_hwpoison_address(addr)) {
+ get_page(hwpoison_page);
+ return page_to_pfn(hwpoison_page);
+ }
+
down_read(&current->mm->mmap_sem);
vma = find_vma(current->mm, addr);
@@ -2197,6 +2211,15 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
bad_pfn = page_to_pfn(bad_page);
+ hwpoison_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+
+ if (hwpoison_page == NULL) {
+ r = -ENOMEM;
+ goto out_free_0;
+ }
+
+ hwpoison_pfn = page_to_pfn(hwpoison_page);
+
if (!zalloc_cpumask_var(&cpus_hardware_enabled, GFP_KERNEL)) {
r = -ENOMEM;
goto out_free_0;
@@ -2269,6 +2292,8 @@ out_free_1:
out_free_0a:
free_cpumask_var(cpus_hardware_enabled);
out_free_0:
+ if (hwpoison_page)
+ __free_page(hwpoison_page);
__free_page(bad_page);
out:
kvm_arch_exit();
@@ -2290,6 +2315,7 @@ void kvm_exit(void)
kvm_arch_hardware_unsetup();
kvm_arch_exit();
free_cpumask_var(cpus_hardware_enabled);
+ __free_page(hwpoison_page);
__free_page(bad_page);
}
EXPORT_SYMBOL_GPL(kvm_exit);

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