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drivers/virt/acrn: fix PFNMAP PTE checks in acrn_vm_ram_map()

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Patch series "mm: follow_pte() improvements and acrn follow_pte() fixes".

Patch #1 fixes a bunch of issues I spotted in the acrn driver.  It
compiles, that's all I know.  I'll appreciate some review and testing from
acrn folks.

Patch #2+#3 improve follow_pte(), passing a VMA instead of the MM, adding
more sanity checks, and improving the documentation.  Gave it a quick test
on x86-64 using VM_PAT that ends up using follow_pte().


This patch (of 3):

We currently miss handling various cases, resulting in a dangerous
follow_pte() (previously follow_pfn()) usage.

(1) We're not checking PTE write permissions.

Maybe we should simply always require pte_write() like we do for
pin_user_pages_fast(FOLL_WRITE)? Hard to tell, so let's check for
ACRN_MEM_ACCESS_WRITE for now.

(2) We're not rejecting refcounted pages.

As we are not using MMU notifiers, messing with refcounted pages is
dangerous and can result in use-after-free. Let's make sure to reject them.

(3) We are only looking at the first PTE of a bigger range.

We only lookup a single PTE, but memmap->len may span a larger area.
Let's loop over all involved PTEs and make sure the PFN range is
actually contiguous. Reject everything else: it couldn't have worked
either way, and rather made use access PFNs we shouldn't be accessing.

Link: https://lkml.kernel.org/r/20240410155527.474777-1-david@redhat.com
Link: https://lkml.kernel.org/r/20240410155527.474777-2-david@redhat.com
Fixes: 8a6e85f75a ("virt: acrn: obtain pa from VMA with PFNMAP flag")
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Fei Li <fei1.li@intel.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Yonghua Huang <yonghua.huang@intel.com>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2024-04-10 17:55:25 +02:00 committed by Andrew Morton
parent d4a34d7fb4
commit 3d6586008f
1 changed files with 47 additions and 16 deletions
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63
drivers/virt/acrn/mm.c
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@ -156,23 +156,29 @@ int acrn_vm_memseg_unmap(struct acrn_vm *vm, struct acrn_vm_memmap *memmap)
int acrn_vm_ram_map(struct acrn_vm *vm, struct acrn_vm_memmap *memmap)
{
struct vm_memory_region_batch *regions_info;
int nr_pages, i = 0, order, nr_regions = 0;
int nr_pages, i, order, nr_regions = 0;
struct vm_memory_mapping *region_mapping;
struct vm_memory_region_op *vm_region;
struct page **pages = NULL, *page;
void *remap_vaddr;
int ret, pinned;
u64 user_vm_pa;
unsigned long pfn;
struct vm_area_struct *vma;
if (!vm || !memmap)
return -EINVAL;
/* Get the page number of the map region */
nr_pages = memmap->len >> PAGE_SHIFT;
if (!nr_pages)
return -EINVAL;
mmap_read_lock(current->mm);
vma = vma_lookup(current->mm, memmap->vma_base);
if (vma && ((vma->vm_flags & VM_PFNMAP) != 0)) {
unsigned long start_pfn, cur_pfn;
spinlock_t *ptl;
bool writable;
pte_t *ptep;
if ((memmap->vma_base + memmap->len) > vma->vm_end) {
@ -180,25 +186,53 @@ int acrn_vm_ram_map(struct acrn_vm *vm, struct acrn_vm_memmap *memmap)
return -EINVAL;
}
ret = follow_pte(vma->vm_mm, memmap->vma_base, &ptep, &ptl);
if (ret < 0) {
mmap_read_unlock(current->mm);
for (i = 0; i < nr_pages; i++) {
ret = follow_pte(vma->vm_mm,
memmap->vma_base + i * PAGE_SIZE,
&ptep, &ptl);
if (ret)
break;
cur_pfn = pte_pfn(ptep_get(ptep));
if (i == 0)
start_pfn = cur_pfn;
writable = !!pte_write(ptep_get(ptep));
pte_unmap_unlock(ptep, ptl);
/* Disallow write access if the PTE is not writable. */
if (!writable &&
(memmap->attr & ACRN_MEM_ACCESS_WRITE)) {
ret = -EFAULT;
break;
}
/* Disallow refcounted pages. */
if (pfn_valid(cur_pfn) &&
!PageReserved(pfn_to_page(cur_pfn))) {
ret = -EFAULT;
break;
}
/* Disallow non-contiguous ranges. */
if (cur_pfn != start_pfn + i) {
ret = -EINVAL;
break;
}
}
mmap_read_unlock(current->mm);
if (ret) {
dev_dbg(acrn_dev.this_device,
"Failed to lookup PFN at VMA:%pK.\n", (void *)memmap->vma_base);
return ret;
}
pfn = pte_pfn(ptep_get(ptep));
pte_unmap_unlock(ptep, ptl);
mmap_read_unlock(current->mm);
return acrn_mm_region_add(vm, memmap->user_vm_pa,
PFN_PHYS(pfn), memmap->len,
PFN_PHYS(start_pfn), memmap->len,
ACRN_MEM_TYPE_WB, memmap->attr);
}
mmap_read_unlock(current->mm);
/* Get the page number of the map region */
nr_pages = memmap->len >> PAGE_SHIFT;
pages = vzalloc(array_size(nr_pages, sizeof(*pages)));
if (!pages)
return -ENOMEM;
@ -242,12 +276,11 @@ int acrn_vm_ram_map(struct acrn_vm *vm, struct acrn_vm_memmap *memmap)
mutex_unlock(&vm->regions_mapping_lock);
/* Calculate count of vm_memory_region_op */
while (i < nr_pages) {
for (i = 0; i < nr_pages; i += 1 << order) {
page = pages[i];
VM_BUG_ON_PAGE(PageTail(page), page);
order = compound_order(page);
nr_regions++;
i += 1 << order;
}
/* Prepare the vm_memory_region_batch */
@ -264,8 +297,7 @@ int acrn_vm_ram_map(struct acrn_vm *vm, struct acrn_vm_memmap *memmap)
regions_info->vmid = vm->vmid;
regions_info->regions_gpa = virt_to_phys(vm_region);
user_vm_pa = memmap->user_vm_pa;
i = 0;
while (i < nr_pages) {
for (i = 0; i < nr_pages; i += 1 << order) {
u32 region_size;
page = pages[i];
@ -281,7 +313,6 @@ int acrn_vm_ram_map(struct acrn_vm *vm, struct acrn_vm_memmap *memmap)
vm_region++;
user_vm_pa += region_size;
i += 1 << order;
}
/* Inform the ACRN Hypervisor to set up EPT mappings */