Messages in this thread | | | Date | Wed, 10 Aug 2022 14:19:51 +0200 | From | Daniel Vetter <> | Subject | Re: [PATCH] virt: acrn: obtain pa from VMA with PFNMAP flag |
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On Mon, Feb 28, 2022 at 05:22:12AM +0300, Yonghua Huang wrote: > acrn_vm_ram_map can't pin the user pages with VM_PFNMAP flag > by calling get_user_pages_fast(), the PA(physical pages) > may be mapped by kernel driver and set PFNMAP flag. > > This patch fixes logic to setup EPT mapping for PFN mapped RAM region > by checking the memory attribute before adding EPT mapping for them. > > Fixes: 88f537d5e8dd ("virt: acrn: Introduce EPT mapping management") > Signed-off-by: Yonghua Huang <yonghua.huang@intel.com> > Signed-off-by: Fei Li <fei1.li@intel.com> > --- > drivers/virt/acrn/mm.c | 24 ++++++++++++++++++++++++ > 1 file changed, 24 insertions(+) > > diff --git a/drivers/virt/acrn/mm.c b/drivers/virt/acrn/mm.c > index c4f2e15c8a2b..3b1b1e7a844b 100644 > --- a/drivers/virt/acrn/mm.c > +++ b/drivers/virt/acrn/mm.c > @@ -162,10 +162,34 @@ int acrn_vm_ram_map(struct acrn_vm *vm, struct acrn_vm_memmap *memmap) > void *remap_vaddr; > int ret, pinned; > u64 user_vm_pa; > + unsigned long pfn; > + struct vm_area_struct *vma; > > if (!vm || !memmap) > return -EINVAL; > > + mmap_read_lock(current->mm); > + vma = vma_lookup(current->mm, memmap->vma_base); > + if (vma && ((vma->vm_flags & VM_PFNMAP) != 0)) { > + if ((memmap->vma_base + memmap->len) > vma->vm_end) { > + mmap_read_unlock(current->mm); > + return -EINVAL; > + } > + > + ret = follow_pfn(vma, memmap->vma_base, &pfn);
This races, don't use follow_pfn() and most definitely don't add new users. In some cases follow_pte, but the pte/pfn is still only valid for as long as you hold the pte spinlock.
> + mmap_read_unlock(current->mm);
Definitely after here there's zero guarantees about this pfn and it could point at anything.
Please fix, I tried pretty hard to get rid of follow_pfn(), but some of them are just too hard to fix (e.g. kvm needs a pretty hug rewrite to get it all sorted).
Cheers, Daniel
> + if (ret < 0) { > + dev_dbg(acrn_dev.this_device, > + "Failed to lookup PFN at VMA:%pK.\n", (void *)memmap->vma_base); > + return ret; > + } > + > + return acrn_mm_region_add(vm, memmap->user_vm_pa, > + PFN_PHYS(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(nr_pages * sizeof(struct page *)); > > base-commit: 73878e5eb1bd3c9656685ca60bc3a49d17311e0c > -- > 2.25.1 >
-- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
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