diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index e458995f2b5da2671af609a9bfae27f1da9dd8b1..76c30f0f7c77c92ec7cfdcc76764477c3880108a 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -960,6 +960,8 @@ ext4_find_extent(struct inode *inode, ext4_lblk_t block,
 
 	ext4_ext_show_path(inode, path);
 
+	if (orig_path)
+		*orig_path = path;
 	return path;
 
 err:
@@ -3260,6 +3262,24 @@ static int ext4_split_extent_at(handle_t *handle,
 	if (err != -ENOSPC && err != -EDQUOT)
 		goto out;
 
+	/*
+	 * Update path is required because previous ext4_ext_insert_extent()
+	 * may have freed or reallocated the path. Using EXT4_EX_NOFAIL
+	 * guarantees that ext4_find_extent() will not return -ENOMEM,
+	 * otherwise -ENOMEM will cause a retry in do_writepages(), and a
+	 * WARN_ON may be triggered in ext4_da_update_reserve_space() due to
+	 * an incorrect ee_len causing the i_reserved_data_blocks exception.
+	 */
+	path = ext4_find_extent(inode, ee_block, ppath,
+				flags | EXT4_EX_NOFAIL);
+	if (IS_ERR(path)) {
+		EXT4_ERROR_INODE(inode, "Failed split extent on %u, err %ld",
+				 split, PTR_ERR(path));
+		return PTR_ERR(path);
+	}
+	depth = ext_depth(inode);
+	ex = path[depth].p_ext;
+
 	if (EXT4_EXT_MAY_ZEROOUT & split_flag) {
 		if (split_flag & (EXT4_EXT_DATA_VALID1|EXT4_EXT_DATA_VALID2)) {
 			if (split_flag & EXT4_EXT_DATA_VALID1) {
@@ -3312,7 +3332,7 @@ static int ext4_split_extent_at(handle_t *handle,
 	ext4_ext_dirty(handle, inode, path + path->p_depth);
 	return err;
 out:
-	ext4_ext_show_leaf(inode, path);
+	ext4_ext_show_leaf(inode, *ppath);
 	return err;
 }
 
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index f8dd5d972c337035b29060f3f5e7e355ad252e60..661a8544d7817ea19aa9a482db552d8025f42bb9 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -36,7 +36,6 @@ get_ext_path(struct inode *inode, ext4_lblk_t lblock,
 		*ppath = NULL;
 		return -ENODATA;
 	}
-	*ppath = path;
 	return 0;
 }
 
diff --git a/mm/mmap.c b/mm/mmap.c
index 14e6bfdebbb82de95dfc3d463d0865642ca6de3f..04919dc9fbbf40938f8e368b5731f028a75994b3 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3040,6 +3040,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 	unsigned long populate = 0;
 	unsigned long ret = -EINVAL;
 	struct file *file;
+	vm_flags_t vm_flags;
 
 	pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/vm/remap_file_pages.rst.\n",
 		     current->comm, current->pid);
@@ -3056,15 +3057,60 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 	if (pgoff + (size >> PAGE_SHIFT) < pgoff)
 		return ret;
 
-	if (mmap_write_lock_killable(mm))
+	if (mmap_read_lock_killable(mm))
 		return -EINTR;
 
-	vma = find_vma(mm, start);
+	/*
+	 * Look up VMA under read lock first so we can perform the security
+	 * without holding locks (which can be problematic). We reacquire a
+	 * write lock later and check nothing changed underneath us.
+	 */
+	vma = vma_lookup(mm, start);
+
+	if (!vma || !(vma->vm_flags & VM_SHARED)) {
+		mmap_read_unlock(mm);
+		return -EINVAL;
+	}
 
-	if (!vma || !(vma->vm_flags & VM_SHARED))
+	prot |= vma->vm_flags & VM_READ ? PROT_READ : 0;
+	prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0;
+	prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0;
+
+	flags &= MAP_NONBLOCK;
+	flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
+	if (vma->vm_flags & VM_LOCKED)
+		flags |= MAP_LOCKED;
+
+	/* Save vm_flags used to calculate prot and flags, and recheck later. */
+	vm_flags = vma->vm_flags;
+	file = get_file(vma->vm_file);
+
+	mmap_read_unlock(mm);
+
+	/* Call outside mmap_lock to be consistent with other callers. */
+	ret = security_mmap_file(file, prot, flags);
+	if (ret) {
+		fput(file);
+		return ret;
+	}
+
+	ret = -EINVAL;
+
+	/* OK security check passed, take write lock + let it rip. */
+	if (mmap_write_lock_killable(mm)) {
+		fput(file);
+		return -EINTR;
+	}
+
+	vma = vma_lookup(mm, start);
+
+	if (!vma)
 		goto out;
 
-	if (start < vma->vm_start)
+	/* Make sure things didn't change under us. */
+	if (vma->vm_flags != vm_flags)
+		goto out;
+	if (vma->vm_file != file)
 		goto out;
 
 	if (start + size > vma->vm_end) {
@@ -3089,37 +3135,11 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 			goto out;
 	}
 
-	prot |= vma->vm_flags & VM_READ ? PROT_READ : 0;
-	prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0;
-	prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0;
-
-	flags &= MAP_NONBLOCK;
-	flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
-	if (vma->vm_flags & VM_LOCKED) {
-		struct vm_area_struct *tmp;
-		flags |= MAP_LOCKED;
-
-		/* drop PG_Mlocked flag for over-mapped range */
-		for (tmp = vma; tmp->vm_start >= start + size;
-				tmp = tmp->vm_next) {
-			/*
-			 * Split pmd and munlock page on the border
-			 * of the range.
-			 */
-			vma_adjust_trans_huge(tmp, start, start + size, 0);
-
-			munlock_vma_pages_range(tmp,
-					max(tmp->vm_start, start),
-					min(tmp->vm_end, start + size));
-		}
-	}
-
-	file = get_file(vma->vm_file);
 	ret = do_mmap(vma->vm_file, start, size,
 			prot, flags, pgoff, &populate, NULL);
-	fput(file);
 out:
 	mmap_write_unlock(mm);
+	fput(file);
 	if (populate)
 		mm_populate(ret, populate);
 	if (!IS_ERR_VALUE(ret))
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 7e3eb0af4b0e3cc4f82a6decef9df1fbcf96d37c..ac746c1a26e136f83ff21c8d025f7bd75127541a 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -174,7 +174,7 @@ static void rt6_uncached_list_flush_dev(struct net *net, struct net_device *dev)
 			struct inet6_dev *rt_idev = rt->rt6i_idev;
 			struct net_device *rt_dev = rt->dst.dev;
 
-			if (rt_idev->dev == dev) {
+			if (rt_idev && rt_idev->dev == dev) {
 				rt->rt6i_idev = in6_dev_get(loopback_dev);
 				in6_dev_put(rt_idev);
 			}