This is a note to let you know that I've just added the patch titled s390/gmap: validate VMA in __gmap_zap() to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: s390-gmap-validate-vma-in-__gmap_zap.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit d20014a393c9a02727204b3789ee45ef732a72c7 Author: David Hildenbrand <david@xxxxxxxxxx> Date: Thu Sep 9 18:22:40 2021 +0200 s390/gmap: validate VMA in __gmap_zap() [ Upstream commit 2d8fb8f3914b40e3cc12f8cbb74daefd5245349d ] We should not walk/touch page tables outside of VMA boundaries when holding only the mmap sem in read mode. Evil user space can modify the VMA layout just before this function runs and e.g., trigger races with page table removal code since commit dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap"). The pure prescence in our guest_to_host radix tree does not imply that there is a VMA. Further, we should not allocate page tables (via get_locked_pte()) outside of VMA boundaries: if evil user space decides to map hugetlbfs to these ranges, bad things will happen because we suddenly have PTE or PMD page tables where we shouldn't have them. Similarly, we have to check if we suddenly find a hugetlbfs VMA, before calling get_locked_pte(). Note that gmap_discard() is different: zap_page_range()->unmap_single_vma() makes sure to stay within VMA boundaries. Fixes: b31288fa83b2 ("s390/kvm: support collaborative memory management") Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> Acked-by: Heiko Carstens <hca@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20210909162248.14969-2-david@xxxxxxxxxx Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c index a29d2e88b00ef..55cf3ed1d1fae 100644 --- a/arch/s390/mm/gmap.c +++ b/arch/s390/mm/gmap.c @@ -654,6 +654,7 @@ EXPORT_SYMBOL_GPL(gmap_fault); */ void __gmap_zap(struct gmap *gmap, unsigned long gaddr) { + struct vm_area_struct *vma; unsigned long vmaddr; spinlock_t *ptl; pte_t *ptep; @@ -663,6 +664,11 @@ void __gmap_zap(struct gmap *gmap, unsigned long gaddr) gaddr >> PMD_SHIFT); if (vmaddr) { vmaddr |= gaddr & ~PMD_MASK; + + vma = vma_lookup(gmap->mm, vmaddr); + if (!vma || is_vm_hugetlb_page(vma)) + return; + /* Get pointer to the page table entry */ ptep = get_locked_pte(gmap->mm, vmaddr, &ptl); if (likely(ptep))