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A selftests fix for ARM, and the fix for page reference count underflow.

Browse source 
This is a very small fix that was provided by Nick Piggin and tested
 by myself.
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Merge tag 'for-linus-urgent' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm fixes from Paolo Bonzini:
 "A selftests fix for ARM, and the fix for page reference count
  underflow. This is a very small fix that was provided by Nick Piggin
  and tested by myself"

* tag 'for-linus-urgent' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: do not allow mapping valid but non-reference-counted pages
  KVM: selftests: Fix mapping length truncation in m{,un}map()
This commit is contained in:
Linus Torvalds 2021-06-25 10:15:35 -07:00
commit 616a99dd14
2 changed files with 19 additions and 4 deletions
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4
tools/testing/selftests/kvm/set_memory_region_test.c
View file

@ -376,7 +376,7 @@ static void test_add_max_memory_regions(void)
pr_info("Adding slots 0..%i, each memory region with %dK size\n",
(max_mem_slots - 1), MEM_REGION_SIZE >> 10);
mem = mmap(NULL, MEM_REGION_SIZE * max_mem_slots + alignment,
mem = mmap(NULL, (size_t)max_mem_slots * MEM_REGION_SIZE + alignment,
PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
TEST_ASSERT(mem != MAP_FAILED, "Failed to mmap() host");
mem_aligned = (void *)(((size_t) mem + alignment - 1) & ~(alignment - 1));
@ -401,7 +401,7 @@ static void test_add_max_memory_regions(void)
TEST_ASSERT(ret == -1 && errno == EINVAL,
"Adding one more memory slot should fail with EINVAL");
munmap(mem, MEM_REGION_SIZE * max_mem_slots + alignment);
munmap(mem, (size_t)max_mem_slots * MEM_REGION_SIZE + alignment);
munmap(mem_extra, MEM_REGION_SIZE);
kvm_vm_free(vm);
}

19
virt/kvm/kvm_main.c
View file

@ -2055,6 +2055,13 @@ static bool vma_is_valid(struct vm_area_struct *vma, bool write_fault)
return true;
}
static int kvm_try_get_pfn(kvm_pfn_t pfn)
{
if (kvm_is_reserved_pfn(pfn))
return 1;
return get_page_unless_zero(pfn_to_page(pfn));
}
static int hva_to_pfn_remapped(struct vm_area_struct *vma,
unsigned long addr, bool *async,
bool write_fault, bool *writable,
@ -2104,13 +2111,21 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma,
* Whoever called remap_pfn_range is also going to call e.g.
* unmap_mapping_range before the underlying pages are freed,
* causing a call to our MMU notifier.
*
* Certain IO or PFNMAP mappings can be backed with valid
* struct pages, but be allocated without refcounting e.g.,
* tail pages of non-compound higher order allocations, which
* would then underflow the refcount when the caller does the
* required put_page. Don't allow those pages here.
*/
kvm_get_pfn(pfn);
if (!kvm_try_get_pfn(pfn))
r = -EFAULT;
out:
pte_unmap_unlock(ptep, ptl);
*p_pfn = pfn;
return 0;
return r;
}
/*