1 files changed, 44 insertions, 8 deletions

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 8bc970748b96..e61aab1999d3 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -701,7 +701,7 @@ static int ovl_create_volatile_dirty(struct ovl_fs *ofs)
 }
 
 static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
-			    const struct path *workpath)
+			    const struct path *workpath, size_t nr_data)
 {
 	struct vfsmount *mnt = ovl_upper_mnt(ofs);
 	struct dentry *workdir;
@@ -765,9 +765,11 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
 	if (err) {
 		pr_warn("failed to set xattr on upper\n");
 		ofs->noxattr = true;
-		if (ovl_redirect_follow(ofs)) {
-			ofs->config.redirect_mode = OVL_REDIRECT_NOFOLLOW;
-			pr_warn("...falling back to redirect_dir=nofollow.\n");
+		if (ovl_redirect_follow_lower(ofs)) {
+			ofs->config.redirect_mode =
+				ovl_redirect_follow_mode(false, nr_data);
+			pr_warn("...falling back to redirect_dir=%s.\n",
+				ovl_redirect_mode(&ofs->config));
 		}
 		if (ofs->config.metacopy) {
 			ofs->config.metacopy = false;
@@ -844,7 +846,7 @@ out:
 
 static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
 			   const struct path *upperpath,
-			   const struct path *workpath)
+			   const struct path *workpath, size_t nr_data)
 {
 	int err;
 
@@ -873,7 +875,7 @@ static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
 	if (err)
 		return err;
 
-	return ovl_make_workdir(sb, ofs, workpath);
+	return ovl_make_workdir(sb, ofs, workpath, nr_data);
 }
 
 static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
@@ -1142,6 +1144,29 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
 		}
 
 		/*
+		 * Lower file handles identify the lower fs, but not the layer,
+		 * so with different idmaps on the same lower fs, index and
+		 * nfs_export may decode a file handle through a layer with the
+		 * wrong idmap.  Following copy up origin without index is only
+		 * used for st_ino, which does not depend on the idmap.
+		 */
+		if (i < nr_merged_lower &&
+		    (ofs->config.index || ofs->config.nfs_export)) {
+			const struct mnt_idmap *idmap = mnt_idmap(mnt);
+			struct ovl_sb *fs = &ofs->fs[fsid];
+
+			if (!fs->lower_idmap) {
+				fs->lower_idmap = idmap;
+			} else if (fs->lower_idmap != idmap) {
+				pr_err("lower layer '%pd2' conflicts with idmap of another lower layer on the same fs, mount with '-o index=off,nfs_export=off' to override.\n",
+				       l->path.dentry);
+				iput(trap);
+				kern_unmount(mnt);
+				return -EINVAL;
+			}
+		}
+
+		/*
 		 * Make lower layers R/O.  That way fchmod/fchown on lower file
 		 * will fail instead of modifying lower fs.
 		 */
@@ -1485,7 +1510,8 @@ static int ovl_fill_super_creds(struct fs_context *fc, struct super_block *sb)
 			}
 		}
 
-		err = ovl_get_workdir(sb, ofs, &ctx->upper, &ctx->work);
+		err = ovl_get_workdir(sb, ofs, &ctx->upper, &ctx->work,
+				      ctx->nr_data);
 		if (err)
 			return err;
 
@@ -1619,13 +1645,23 @@ out_err:
 	return err;
 }
 
+static void ovl_kill_sb(struct super_block *sb)
+{
+	struct ovl_fs *ofs = OVL_FS(sb);
+
+	/* Nothing can modify them now, do not hold them across the sync */
+	if (ofs)
+		ovl_inuse_unlock_all(ofs);
+	kill_anon_super(sb);
+}
+
 struct file_system_type ovl_fs_type = {
 	.owner			= THIS_MODULE,
 	.name			= "overlay",
 	.init_fs_context	= ovl_init_fs_context,
 	.parameters		= ovl_parameter_spec,
 	.fs_flags		= FS_USERNS_MOUNT | FS_ALLOW_IDMAP,
-	.kill_sb		= kill_anon_super,
+	.kill_sb		= ovl_kill_sb,
 };
 MODULE_ALIAS_FS("overlay");