Merge branch 'akpm' (patches from Andrew)

Merge misc fixes from Andrew Morton:
 "8 patches.

  Subsystems affected by this patch series: mm (hugetlb, pagemap, and
  userfaultfd), memfd, selftests, and kconfig"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  configs/debug: set CONFIG_DEBUG_INFO=y properly
  proc: fix documentation and description of pagemap
  kselftest/vm: fix tests build with old libc
  memfd: fix F_SEAL_WRITE after shmem huge page allocated
  mm: fix use-after-free when anon vma name is used after vma is freed
  mm: prevent vm_area_struct::anon_name refcount saturation
  mm: refactor vm_area_struct::anon_vma_name usage code
  selftests/vm: cleanup hugetlb file after mremap test

3 files changed, 77 insertions, 32 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 213cc569b192..5744a3fc4716 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2626,7 +2626,7 @@ static inline int vma_adjust(struct vm_area_struct *vma, unsigned long start,
 extern struct vm_area_struct *vma_merge(struct mm_struct *,
 	struct vm_area_struct *prev, unsigned long addr, unsigned long end,
 	unsigned long vm_flags, struct anon_vma *, struct file *, pgoff_t,
-	struct mempolicy *, struct vm_userfaultfd_ctx, const char *);
+	struct mempolicy *, struct vm_userfaultfd_ctx, struct anon_vma_name *);
 extern struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *);
 extern int __split_vma(struct mm_struct *, struct vm_area_struct *,
 	unsigned long addr, int new_below);
@@ -3372,11 +3372,12 @@ static inline int seal_check_future_write(int seals, struct vm_area_struct *vma)
 
 #ifdef CONFIG_ANON_VMA_NAME
 int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
-			  unsigned long len_in, const char *name);
+			  unsigned long len_in,
+			  struct anon_vma_name *anon_name);
 #else
 static inline int
 madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
-		      unsigned long len_in, const char *name) {
+		      unsigned long len_in, struct anon_vma_name *anon_name) {
 	return 0;
 }
 #endif
diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index b725839dfe71..cf90b1fa2c60 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -140,50 +140,91 @@ static __always_inline void del_page_from_lru_list(struct page *page,
 
 #ifdef CONFIG_ANON_VMA_NAME
 /*
- * mmap_lock should be read-locked when calling vma_anon_name() and while using
- * the returned pointer.
+ * mmap_lock should be read-locked when calling anon_vma_name(). Caller should
+ * either keep holding the lock while using the returned pointer or it should
+ * raise anon_vma_name refcount before releasing the lock.
  */
-extern const char *vma_anon_name(struct vm_area_struct *vma);
+extern struct anon_vma_name *anon_vma_name(struct vm_area_struct *vma);
+extern struct anon_vma_name *anon_vma_name_alloc(const char *name);
+extern void anon_vma_name_free(struct kref *kref);
 
-/*
- * mmap_lock should be read-locked for orig_vma->vm_mm.
- * mmap_lock should be write-locked for new_vma->vm_mm or new_vma should be
- * isolated.
- */
-extern void dup_vma_anon_name(struct vm_area_struct *orig_vma,
-			      struct vm_area_struct *new_vma);
+/* mmap_lock should be read-locked */
+static inline void anon_vma_name_get(struct anon_vma_name *anon_name)
+{
+	if (anon_name)
+		kref_get(&anon_name->kref);
+}
 
-/*
- * mmap_lock should be write-locked or vma should have been isolated under
- * write-locked mmap_lock protection.
- */
-extern void free_vma_anon_name(struct vm_area_struct *vma);
+static inline void anon_vma_name_put(struct anon_vma_name *anon_name)
+{
+	if (anon_name)
+		kref_put(&anon_name->kref, anon_vma_name_free);
+}
 
-/* mmap_lock should be read-locked */
-static inline bool is_same_vma_anon_name(struct vm_area_struct *vma,
-					 const char *name)
+static inline
+struct anon_vma_name *anon_vma_name_reuse(struct anon_vma_name *anon_name)
+{
+	/* Prevent anon_name refcount saturation early on */
+	if (kref_read(&anon_name->kref) < REFCOUNT_MAX) {
+		anon_vma_name_get(anon_name);
+		return anon_name;
+
+	}
+	return anon_vma_name_alloc(anon_name->name);
+}
+
+static inline void dup_anon_vma_name(struct vm_area_struct *orig_vma,
+				     struct vm_area_struct *new_vma)
+{
+	struct anon_vma_name *anon_name = anon_vma_name(orig_vma);
+
+	if (anon_name)
+		new_vma->anon_name = anon_vma_name_reuse(anon_name);
+}
+
+static inline void free_anon_vma_name(struct vm_area_struct *vma)
 {
-	const char *vma_name = vma_anon_name(vma);
+	/*
+	 * Not using anon_vma_name because it generates a warning if mmap_lock
+	 * is not held, which might be the case here.
+	 */
+	if (!vma->vm_file)
+		anon_vma_name_put(vma->anon_name);
+}
 
-	/* either both NULL, or pointers to same string */
-	if (vma_name == name)
+static inline bool anon_vma_name_eq(struct anon_vma_name *anon_name1,
+				    struct anon_vma_name *anon_name2)
+{
+	if (anon_name1 == anon_name2)
 		return true;
 
-	return name && vma_name && !strcmp(name, vma_name);
+	return anon_name1 && anon_name2 &&
+		!strcmp(anon_name1->name, anon_name2->name);
 }
+
 #else /* CONFIG_ANON_VMA_NAME */
-static inline const char *vma_anon_name(struct vm_area_struct *vma)
+static inline struct anon_vma_name *anon_vma_name(struct vm_area_struct *vma)
 {
 	return NULL;
 }
-static inline void dup_vma_anon_name(struct vm_area_struct *orig_vma,
-			      struct vm_area_struct *new_vma) {}
-static inline void free_vma_anon_name(struct vm_area_struct *vma) {}
-static inline bool is_same_vma_anon_name(struct vm_area_struct *vma,
-					 const char *name)
+
+static inline struct anon_vma_name *anon_vma_name_alloc(const char *name)
+{
+	return NULL;
+}
+
+static inline void anon_vma_name_get(struct anon_vma_name *anon_name) {}
+static inline void anon_vma_name_put(struct anon_vma_name *anon_name) {}
+static inline void dup_anon_vma_name(struct vm_area_struct *orig_vma,
+				     struct vm_area_struct *new_vma) {}
+static inline void free_anon_vma_name(struct vm_area_struct *vma) {}
+
+static inline bool anon_vma_name_eq(struct anon_vma_name *anon_name1,
+				    struct anon_vma_name *anon_name2)
 {
 	return true;
 }
+
 #endif  /* CONFIG_ANON_VMA_NAME */
 
 static inline void init_tlb_flush_pending(struct mm_struct *mm)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5140e5feb486..0f549870da6a 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -416,7 +416,10 @@ struct vm_area_struct {
 			struct rb_node rb;
 			unsigned long rb_subtree_last;
 		} shared;
-		/* Serialized by mmap_sem. */
+		/*
+		 * Serialized by mmap_sem. Never use directly because it is
+		 * valid only when vm_file is NULL. Use anon_vma_name instead.
+		 */
 		struct anon_vma_name *anon_name;
 	};