userfaultfd: propagate the full address in THP faults

Orabug: 21685254

The THP faults were not propagating the original fault address.  The
latest version of the API with uffd.arg.pagefault.address is supposed to
propagate the full address through THP faults.

This was not a kernel crashing bug and it wouldn't risk to corrupt user
memory, but it would cause a SIGBUS failure because the wrong page was
being copied.

For various reasons this wasn't easily reproducible in the qemu workload,
but the strestest exposed the problem immediately.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 230c92a8797e0e717c6732de0fffdd5726c0f48f)
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Dhaval Giani <dhaval.giani@oracle.com>
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e68b8db89ed3ad509aefd90d1f19ec0793b00c4f..c02a2d0afc2aa167eb8407afb600ec59c37313c0 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -717,13 +717,14 @@ static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
 
 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
                                        struct vm_area_struct *vma,
-                                       unsigned long haddr, pmd_t *pmd,
+                                       unsigned long address, pmd_t *pmd,
                                        struct page *page, gfp_t gfp,
                                        unsigned int flags)
 {
        struct mem_cgroup *memcg;
        pgtable_t pgtable;
        spinlock_t *ptl;
+       unsigned long haddr = address & HPAGE_PMD_MASK;
 
        VM_BUG_ON_PAGE(!PageCompound(page), page);
 
@@ -765,7 +766,7 @@ static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
                        mem_cgroup_cancel_charge(page, memcg);
                        put_page(page);
                        pte_free(mm, pgtable);
-                       ret = handle_userfault(vma, haddr, flags,
+                       ret = handle_userfault(vma, address, flags,
                                               VM_UFFD_MISSING);
                        VM_BUG_ON(ret & VM_FAULT_FALLBACK);
                        return ret;
@@ -841,7 +842,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
                if (pmd_none(*pmd)) {
                        if (userfaultfd_missing(vma)) {
                                spin_unlock(ptl);
-                               ret = handle_userfault(vma, haddr, flags,
+                               ret = handle_userfault(vma, address, flags,
                                                       VM_UFFD_MISSING);
                                VM_BUG_ON(ret & VM_FAULT_FALLBACK);
                        } else {
@@ -865,7 +866,8 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
                count_vm_event(THP_FAULT_FALLBACK);
                return VM_FAULT_FALLBACK;
        }
-       return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page, gfp, flags);
+       return __do_huge_pmd_anonymous_page(mm, vma, address, pmd, page, gfp,
+                                           flags);
 }
 
 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,