6.6-stable review patch. If anyone has any objections, please let me know.
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From: David Hildenbrand david@redhat.com
[ Upstream commit 3d6586008f7b638f91f3332602592caa8b00b559 ]
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: 8a6e85f75a83 ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/virt/acrn/mm.c | 63 +++++++++++++++++++++++++++++++----------- 1 file changed, 47 insertions(+), 16 deletions(-)
diff --git a/drivers/virt/acrn/mm.c b/drivers/virt/acrn/mm.c index ffc1d1136f765..8ef49d7be453c 100644 --- a/drivers/virt/acrn/mm.c +++ b/drivers/virt/acrn/mm.c @@ -155,23 +155,29 @@ 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) { @@ -179,25 +185,53 @@ 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; @@ -241,12 +275,11 @@ 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 */ @@ -263,8 +296,7 @@ int acrn_vm_ram_map(struct acrn_vm *vm, struct acrn_vm_memmap *memmap) regions_info->regions_num = nr_regions; 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]; @@ -280,7 +312,6 @@ 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 */