mm: page_vma_mapped_walk: map_pte() use pte_offset_map_rw_nolock()

In the caller of map_pte(), we may modify the pvmw->pte after acquiring
the pvmw->ptl, so convert it to using pte_offset_map_rw_nolock().  At this
time, the pte_same() check is not performed after the pvmw->ptl held, so
we should get pmdval and do pmd_same() check to ensure the stability of
pvmw->pmd.

Link: https://lkml.kernel.org/r/2620a48f34c9f19864ab0169cdbf253d31a8fcaa.1727332572.git.zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index ae5cc42aa2087a42fcaa8b1642e53690b2c8c2f9..ab1671e71cb2dfdc5d45747dbe50d992d4dacfb6 100644 (file)
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -13,7 +13,8 @@ static inline bool not_found(struct page_vma_mapped_walk *pvmw)
        return false;
 }
 
-static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)
+static bool map_pte(struct page_vma_mapped_walk *pvmw, pmd_t *pmdvalp,
+                   spinlock_t **ptlp)
 {
        pte_t ptent;
 
@@ -25,6 +26,7 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)
                return !!pvmw->pte;
        }
 
+again:
        /*
         * It is important to return the ptl corresponding to pte,
         * in case *pvmw->pmd changes underneath us; so we need to
@@ -32,8 +34,8 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)
         * proceeds to loop over next ptes, and finds a match later.
         * Though, in most cases, page lock already protects this.
         */
-       pvmw->pte = pte_offset_map_nolock(pvmw->vma->vm_mm, pvmw->pmd,
-                                         pvmw->address, ptlp);
+       pvmw->pte = pte_offset_map_rw_nolock(pvmw->vma->vm_mm, pvmw->pmd,
+                                            pvmw->address, pmdvalp, ptlp);
        if (!pvmw->pte)
                return false;
 
@@ -67,8 +69,13 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)
        } else if (!pte_present(ptent)) {
                return false;
        }
+       spin_lock(*ptlp);
+       if (unlikely(!pmd_same(*pmdvalp, pmdp_get_lockless(pvmw->pmd)))) {
+               pte_unmap_unlock(pvmw->pte, *ptlp);
+               goto again;
+       }
        pvmw->ptl = *ptlp;
-       spin_lock(pvmw->ptl);
+
        return true;
 }
 
@@ -278,7 +285,7 @@ restart:
                        step_forward(pvmw, PMD_SIZE);
                        continue;
                }
-               if (!map_pte(pvmw, &ptl)) {
+               if (!map_pte(pvmw, &pmde, &ptl)) {
                        if (!pvmw->pte)
                                goto restart;
                        goto next_pte;
@@ -305,8 +312,13 @@ next_pte:
                } while (pte_none(ptep_get(pvmw->pte)));
 
                if (!pvmw->ptl) {
+                       spin_lock(ptl);
+                       if (unlikely(!pmd_same(pmde, pmdp_get_lockless(pvmw->pmd)))) {
+                               pte_unmap_unlock(pvmw->pte, ptl);
+                               pvmw->pte = NULL;
+                               goto restart;
+                       }
                        pvmw->ptl = ptl;
-                       spin_lock(pvmw->ptl);
                }
                goto this_pte;
        } while (pvmw->address < end);