Merge branch 'akpm/master' into master

4 files changed, 32 insertions, 4 deletions

diff --git a/fs/exec.c b/fs/exec.c
index 547a2390baf5..f7009df270aa 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1000,6 +1000,14 @@ static int exec_mmap(struct mm_struct *mm)
 		}
 	}
 
+#if defined(CONFIG_LOCKDEP) || defined(CONFIG_DEBUG_VM)
+	/*
+	 * From here on, the mm may be accessed concurrently, and proper locking
+	 * is required for things like get_user_pages_remote().
+	 */
+	mm->mmap_lock_required = 1;
+#endif
+
 	task_lock(tsk);
 	membarrier_exec_mmap(mm);
 
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5a9238f6caad..ae891c0c55fc 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -556,6 +556,16 @@ struct mm_struct {
 #ifdef CONFIG_IOMMU_SUPPORT
 		u32 pasid;
 #endif
+
+#if defined(CONFIG_LOCKDEP) || defined(CONFIG_DEBUG_VM)
+		/*
+		 * Notes whether this mm has been installed on a process yet.
+		 * If not, only the task going through execve() can access this
+		 * mm, and no locking is needed around get_user_pages_remote().
+		 * This flag is only used for debug checks.
+		 */
+		bool mmap_lock_required;
+#endif
 	} __randomize_layout;
 
 	/*
diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
index 18e7eae9b5ba..e1afb420fc94 100644
--- a/include/linux/mmap_lock.h
+++ b/include/linux/mmap_lock.h
@@ -77,14 +77,22 @@ static inline void mmap_read_unlock_non_owner(struct mm_struct *mm)
 
 static inline void mmap_assert_locked(struct mm_struct *mm)
 {
-	lockdep_assert_held(&mm->mmap_lock);
-	VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
+#if defined(CONFIG_LOCKDEP) || defined(CONFIG_DEBUG_VM)
+	if (mm->mmap_lock_required) {
+		lockdep_assert_held(&mm->mmap_lock);
+		VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
+	}
+#endif
 }
 
 static inline void mmap_assert_write_locked(struct mm_struct *mm)
 {
-	lockdep_assert_held_write(&mm->mmap_lock);
-	VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
+#if defined(CONFIG_LOCKDEP) || defined(CONFIG_DEBUG_VM)
+	if (mm->mmap_lock_required) {
+		lockdep_assert_held_write(&mm->mmap_lock);
+		VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
+	}
+#endif
 }
 
 static inline int mmap_lock_is_contended(struct mm_struct *mm)
diff --git a/mm/gup.c b/mm/gup.c
index 102877ed77a4..04e184068ccb 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1027,6 +1027,8 @@ static long __get_user_pages(struct mm_struct *mm,
 	struct vm_area_struct *vma = NULL;
 	struct follow_page_context ctx = { NULL };
 
+	mmap_assert_locked(mm);
+
 	if (!nr_pages)
 		return 0;