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

Documentation/admin-guide/mm/pagemap.rst

@@ -23,7 +23,7 @@ There are four components to pagemap:
     * Bit  56    page exclusively mapped (since 4.2)
     * Bit  57    pte is uffd-wp write-protected (since 5.13) (see
       :ref:`Documentation/admin-guide/mm/userfaultfd.rst <userfaultfd>`)
-    * Bits 57-60 zero
+    * Bits 58-60 zero
     * Bit  61    page is file-page or shared-anon (since 3.5)
     * Bit  62    page swapped
     * Bit  63    page present

fs/proc/task_mmu.c

@@ -309,7 +309,7 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
 
 	name = arch_vma_name(vma);
 	if (!name) {
-		const char *anon_name;
+		struct anon_vma_name *anon_name;
 
 		if (!mm) {
 			name = "[vdso]";
@@ -327,10 +327,10 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
 			goto done;
 		}
 
-		anon_name = vma_anon_name(vma);
+		anon_name = anon_vma_name(vma);
 		if (anon_name) {
 			seq_pad(m, ' ');
-			seq_printf(m, "[anon:%s]", anon_name);
+			seq_printf(m, "[anon:%s]", anon_name->name);
 		}
 	}
 
@@ -1597,7 +1597,8 @@ static const struct mm_walk_ops pagemap_ops = {
  * Bits 5-54  swap offset if swapped
  * Bit  55    pte is soft-dirty (see Documentation/admin-guide/mm/soft-dirty.rst)
  * Bit  56    page exclusively mapped
- * Bits 57-60 zero
+ * Bit  57    pte is uffd-wp write-protected
+ * Bits 58-60 zero
  * Bit  61    page is file-page or shared-anon
  * Bit  62    page swapped
  * Bit  63    page present

fs/userfaultfd.c

@@ -878,7 +878,7 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
 				 new_flags, vma->anon_vma,
 				 vma->vm_file, vma->vm_pgoff,
 				 vma_policy(vma),
-				 NULL_VM_UFFD_CTX, vma_anon_name(vma));
+				 NULL_VM_UFFD_CTX, anon_vma_name(vma));
 		if (prev)
 			vma = prev;
 		else
@@ -1438,7 +1438,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 				 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
 				 vma_policy(vma),
 				 ((struct vm_userfaultfd_ctx){ ctx }),
-				 vma_anon_name(vma));
+				 anon_vma_name(vma));
 		if (prev) {
 			vma = prev;
 			goto next;
@@ -1615,7 +1615,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
 		prev = vma_merge(mm, prev, start, vma_end, new_flags,
 				 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
 				 vma_policy(vma),
-				 NULL_VM_UFFD_CTX, vma_anon_name(vma));
+				 NULL_VM_UFFD_CTX, anon_vma_name(vma));
 		if (prev) {
 			vma = prev;
 			goto next;

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

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)

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;
 	};
 

kernel/configs/debug.config

@@ -16,7 +16,7 @@ CONFIG_SYMBOLIC_ERRNAME=y
 #
 # Compile-time checks and compiler options
 #
-CONFIG_DEBUG_INFO=y
+CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y
 CONFIG_DEBUG_SECTION_MISMATCH=y
 CONFIG_FRAME_WARN=2048
 CONFIG_SECTION_MISMATCH_WARN_ONLY=y

kernel/fork.c

@@ -366,14 +366,14 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
 		*new = data_race(*orig);
 		INIT_LIST_HEAD(&new->anon_vma_chain);
 		new->vm_next = new->vm_prev = NULL;
-		dup_vma_anon_name(orig, new);
+		dup_anon_vma_name(orig, new);
 	}
 	return new;
 }
 
 void vm_area_free(struct vm_area_struct *vma)
 {
-	free_vma_anon_name(vma);
+	free_anon_vma_name(vma);
 	kmem_cache_free(vm_area_cachep, vma);
 }
 

kernel/sys.c

@@ -7,6 +7,7 @@
 
 #include <linux/export.h>
 #include <linux/mm.h>
+#include <linux/mm_inline.h>
 #include <linux/utsname.h>
 #include <linux/mman.h>
 #include <linux/reboot.h>
@@ -2286,15 +2287,16 @@ static int prctl_set_vma(unsigned long opt, unsigned long addr,
 {
 	struct mm_struct *mm = current->mm;
 	const char __user *uname;
-	char *name, *pch;
+	struct anon_vma_name *anon_name = NULL;
 	int error;
 
 	switch (opt) {
 	case PR_SET_VMA_ANON_NAME:
 		uname = (const char __user *)arg;
 		if (uname) {
-			name = strndup_user(uname, ANON_VMA_NAME_MAX_LEN);
+			char *name, *pch;
 
+			name = strndup_user(uname, ANON_VMA_NAME_MAX_LEN);
 			if (IS_ERR(name))
 				return PTR_ERR(name);
 
@@ -2304,15 +2306,18 @@ static int prctl_set_vma(unsigned long opt, unsigned long addr,
 					return -EINVAL;
 				}
 			}
-		} else {
-			/* Reset the name */
-			name = NULL;
+			/* anon_vma has its own copy */
+			anon_name = anon_vma_name_alloc(name);
+			kfree(name);
+			if (!anon_name)
+				return -ENOMEM;
+
 		}
 
 		mmap_write_lock(mm);
-		error = madvise_set_anon_name(mm, addr, size, name);
+		error = madvise_set_anon_name(mm, addr, size, anon_name);
 		mmap_write_unlock(mm);
-		kfree(name);
+		anon_vma_name_put(anon_name);
 		break;
 	default:
 		error = -EINVAL;