Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs updates from Miklos Szeredi:
 "Various fixes and tweaks"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: cleanup unused var in rename2
  ovl: rename is_merge to is_lowest
  ovl: fixed coding style warning
  ovl: Ensure upper filesystem supports d_type
  ovl: Warn on copy up if a process has a R/O fd open to the lower file
  ovl: honor flag MS_SILENT at mount
  ovl: verify upper dentry before unlink and rename

fs/overlayfs/copy_up.c

@@ -7,6 +7,7 @@
  * the Free Software Foundation.
  */
 
+#include <linux/module.h>
 #include <linux/fs.h>
 #include <linux/slab.h>
 #include <linux/file.h>
@@ -16,10 +17,41 @@
 #include <linux/uaccess.h>
 #include <linux/sched.h>
 #include <linux/namei.h>
+#include <linux/fdtable.h>
+#include <linux/ratelimit.h>
 #include "overlayfs.h"
 
 #define OVL_COPY_UP_CHUNK_SIZE (1 << 20)
 
+static bool __read_mostly ovl_check_copy_up;
+module_param_named(check_copy_up, ovl_check_copy_up, bool,
+		   S_IWUSR | S_IRUGO);
+MODULE_PARM_DESC(ovl_check_copy_up,
+		 "Warn on copy-up when causing process also has a R/O fd open");
+
+static int ovl_check_fd(const void *data, struct file *f, unsigned int fd)
+{
+	const struct dentry *dentry = data;
+
+	if (f->f_inode == d_inode(dentry))
+		pr_warn_ratelimited("overlayfs: Warning: Copying up %pD, but open R/O on fd %u which will cease to be coherent [pid=%d %s]\n",
+				    f, fd, current->pid, current->comm);
+	return 0;
+}
+
+/*
+ * Check the fds open by this process and warn if something like the following
+ * scenario is about to occur:
+ *
+ *	fd1 = open("foo", O_RDONLY);
+ *	fd2 = open("foo", O_RDWR);
+ */
+static void ovl_do_check_copy_up(struct dentry *dentry)
+{
+	if (ovl_check_copy_up)
+		iterate_fd(current->files, 0, ovl_check_fd, dentry);
+}
+
 int ovl_copy_xattr(struct dentry *old, struct dentry *new)
 {
 	ssize_t list_size, size, value_size = 0;
@@ -235,6 +267,7 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
 
 	if (S_ISREG(stat->mode)) {
 		struct path upperpath;
+
 		ovl_path_upper(dentry, &upperpath);
 		BUG_ON(upperpath.dentry != NULL);
 		upperpath.dentry = newdentry;
@@ -309,6 +342,8 @@ int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
 	if (WARN_ON(!workdir))
 		return -EROFS;
 
+	ovl_do_check_copy_up(lowerpath->dentry);
+
 	ovl_path_upper(parent, &parentpath);
 	upperdir = parentpath.dentry;
 

fs/overlayfs/dir.c

@@ -596,21 +596,25 @@ static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
 {
 	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 	struct inode *dir = upperdir->d_inode;
-	struct dentry *upper = ovl_dentry_upper(dentry);
+	struct dentry *upper;
 	int err;
 
 	inode_lock_nested(dir, I_MUTEX_PARENT);
+	upper = lookup_one_len(dentry->d_name.name, upperdir,
+			       dentry->d_name.len);
+	err = PTR_ERR(upper);
+	if (IS_ERR(upper))
+		goto out_unlock;
+
 	err = -ESTALE;
-	if (upper->d_parent == upperdir) {
-		/* Don't let d_delete() think it can reset d_inode */
-		dget(upper);
+	if (upper == ovl_dentry_upper(dentry)) {
 		if (is_dir)
 			err = vfs_rmdir(dir, upper);
 		else
 			err = vfs_unlink(dir, upper, NULL);
-		dput(upper);
 		ovl_dentry_version_inc(dentry->d_parent);
 	}
+	dput(upper);
 
 	/*
 	 * Keeping this dentry hashed would mean having to release
@@ -620,6 +624,7 @@ static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
 	 */
 	if (!err)
 		d_drop(dentry);
+out_unlock:
 	inode_unlock(dir);
 
 	return err;
@@ -714,7 +719,6 @@ static int ovl_rename2(struct inode *olddir, struct dentry *old,
 	struct dentry *trap;
 	bool old_opaque;
 	bool new_opaque;
-	bool new_create = false;
 	bool cleanup_whiteout = false;
 	bool overwrite = !(flags & RENAME_EXCHANGE);
 	bool is_dir = d_is_dir(old);
@@ -840,29 +844,38 @@ static int ovl_rename2(struct inode *olddir, struct dentry *old,
 
 	trap = lock_rename(new_upperdir, old_upperdir);
 
-	olddentry = ovl_dentry_upper(old);
-	newdentry = ovl_dentry_upper(new);
-	if (newdentry) {
-		if (opaquedir) {
-			newdentry = opaquedir;
-			opaquedir = NULL;
-		} else {
-			dget(newdentry);
-		}
-	} else {
-		new_create = true;
+
+	olddentry = lookup_one_len(old->d_name.name, old_upperdir,
+				   old->d_name.len);
+	err = PTR_ERR(olddentry);
+	if (IS_ERR(olddentry))
+		goto out_unlock;
+
+	err = -ESTALE;
+	if (olddentry != ovl_dentry_upper(old))
+		goto out_dput_old;
+
 	newdentry = lookup_one_len(new->d_name.name, new_upperdir,
 				   new->d_name.len);
 	err = PTR_ERR(newdentry);
 	if (IS_ERR(newdentry))
-			goto out_unlock;
-	}
+		goto out_dput_old;
 
 	err = -ESTALE;
-	if (olddentry->d_parent != old_upperdir)
+	if (ovl_dentry_upper(new)) {
+		if (opaquedir) {
+			if (newdentry != opaquedir)
 				goto out_dput;
-	if (newdentry->d_parent != new_upperdir)
+		} else {
+			if (newdentry != ovl_dentry_upper(new))
 				goto out_dput;
+		}
+	} else {
+		if (!d_is_negative(newdentry) &&
+		    (!new_opaque || !ovl_is_whiteout(newdentry)))
+			goto out_dput;
+	}
+
 	if (olddentry == trap)
 		goto out_dput;
 	if (newdentry == trap)
@@ -925,6 +938,8 @@ static int ovl_rename2(struct inode *olddir, struct dentry *old,
 
 out_dput:
 	dput(newdentry);
+out_dput_old:
+	dput(olddentry);
 out_unlock:
 	unlock_rename(new_upperdir, old_upperdir);
 out_revert_creds:

fs/overlayfs/overlayfs.h

@@ -166,6 +166,7 @@ extern const struct file_operations ovl_dir_operations;
 int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list);
 void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list);
 void ovl_cache_free(struct list_head *list);
+int ovl_check_d_type_supported(struct path *realpath);
 
 /* inode.c */
 int ovl_setattr(struct dentry *dentry, struct iattr *attr);

fs/overlayfs/readdir.c

@@ -36,13 +36,14 @@ struct ovl_dir_cache {
 
 struct ovl_readdir_data {
 	struct dir_context ctx;
-	bool is_merge;
+	bool is_lowest;
 	struct rb_root root;
 	struct list_head *list;
 	struct list_head middle;
 	struct ovl_cache_entry *first_maybe_whiteout;
 	int count;
 	int err;
+	bool d_type_supported;
 };
 
 struct ovl_dir_file {
@@ -139,7 +140,7 @@ static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
 	return 0;
 }
 
-static int ovl_fill_lower(struct ovl_readdir_data *rdd,
+static int ovl_fill_lowest(struct ovl_readdir_data *rdd,
 			   const char *name, int namelen,
 			   loff_t offset, u64 ino, unsigned int d_type)
 {
@@ -193,10 +194,10 @@ static int ovl_fill_merge(struct dir_context *ctx, const char *name,
 		container_of(ctx, struct ovl_readdir_data, ctx);
 
 	rdd->count++;
-	if (!rdd->is_merge)
+	if (!rdd->is_lowest)
 		return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type);
 	else
-		return ovl_fill_lower(rdd, name, namelen, offset, ino, d_type);
+		return ovl_fill_lowest(rdd, name, namelen, offset, ino, d_type);
 }
 
 static int ovl_check_whiteouts(struct dentry *dir, struct ovl_readdir_data *rdd)
@@ -289,7 +290,7 @@ static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list)
 		.ctx.actor = ovl_fill_merge,
 		.list = list,
 		.root = RB_ROOT,
-		.is_merge = false,
+		.is_lowest = false,
 	};
 	int idx, next;
 
@@ -306,7 +307,7 @@ static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list)
 			 * allows offsets to be reasonably constant
 			 */
 			list_add(&rdd.middle, rdd.list);
-			rdd.is_merge = true;
+			rdd.is_lowest = true;
 			err = ovl_dir_read(&realpath, &rdd);
 			list_del(&rdd.middle);
 		}
@@ -577,3 +578,39 @@ void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list)
 	}
 	inode_unlock(upper->d_inode);
 }
+
+static int ovl_check_d_type(struct dir_context *ctx, const char *name,
+			  int namelen, loff_t offset, u64 ino,
+			  unsigned int d_type)
+{
+	struct ovl_readdir_data *rdd =
+		container_of(ctx, struct ovl_readdir_data, ctx);
+
+	/* Even if d_type is not supported, DT_DIR is returned for . and .. */
+	if (!strncmp(name, ".", namelen) || !strncmp(name, "..", namelen))
+		return 0;
+
+	if (d_type != DT_UNKNOWN)
+		rdd->d_type_supported = true;
+
+	return 0;
+}
+
+/*
+ * Returns 1 if d_type is supported, 0 not supported/unknown. Negative values
+ * if error is encountered.
+ */
+int ovl_check_d_type_supported(struct path *realpath)
+{
+	int err;
+	struct ovl_readdir_data rdd = {
+		.ctx.actor = ovl_check_d_type,
+		.d_type_supported = false,
+	};
+
+	err = ovl_dir_read(realpath, &rdd);
+	if (err)
+		return err;
+
+	return rdd.d_type_supported;
+}

fs/overlayfs/super.c

@@ -936,6 +936,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 
 	err = -EINVAL;
 	if (!ufs->config.lowerdir) {
+		if (!silent)
 			pr_err("overlayfs: missing 'lowerdir'\n");
 		goto out_free_config;
 	}
@@ -1028,6 +1029,21 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 			sb->s_flags |= MS_RDONLY;
 			ufs->workdir = NULL;
 		}
+
+		/*
+		 * Upper should support d_type, else whiteouts are visible.
+		 * Given workdir and upper are on same fs, we can do
+		 * iterate_dir() on workdir.
+		 */
+		err = ovl_check_d_type_supported(&workpath);
+		if (err < 0)
+			goto out_put_workdir;
+
+		if (!err) {
+			pr_err("overlayfs: upper fs needs to support d_type.\n");
+			err = -EINVAL;
+			goto out_put_workdir;
+		}
 	}
 
 	err = -ENOMEM;