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From:   Andrea Righi <andrea.righi@canonical.com>
To:     Miklos Szeredi <miklos@szeredi.hu>
Cc:     linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] ovl: make consistent use of OVL_FS()
Date:   Sat, 20 May 2023 14:05:28 +0200
Message-Id: <20230520120528.339680-1-andrea.righi@canonical.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Always use OVL_FS() to retrieve the corresponding struct ovl_fs from a
struct super_block and make sure that it is exclusively used with an
overlayfs superblock (otherwise, trigger a BUG).

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
---
 fs/overlayfs/copy_up.c   |  2 +-
 fs/overlayfs/export.c    | 10 +++++-----
 fs/overlayfs/inode.c     |  8 ++++----
 fs/overlayfs/namei.c     |  2 +-
 fs/overlayfs/ovl_entry.h |  4 ++++
 fs/overlayfs/super.c     | 10 +++++-----
 fs/overlayfs/util.c      | 18 +++++++++---------
 7 files changed, 29 insertions(+), 25 deletions(-)

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index f658cc8ea492..60aa615820e7 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -905,7 +905,7 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
 static bool ovl_need_meta_copy_up(struct dentry *dentry, umode_t mode,
 				  int flags)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 
 	if (!ofs->config.metacopy)
 		return false;
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index defd4e231ad2..f5f0ef8e3ce8 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -182,7 +182,7 @@ static int ovl_connect_layer(struct dentry *dentry)
  */
 static int ovl_check_encode_origin(struct dentry *dentry)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 
 	/* Upper file handle for pure upper */
 	if (!ovl_dentry_lower(dentry))
@@ -434,7 +434,7 @@ static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
 					    struct dentry *real,
 					    const struct ovl_layer *layer)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 	struct dentry *index = NULL;
 	struct dentry *this = NULL;
 	struct inode *inode;
@@ -655,7 +655,7 @@ static struct dentry *ovl_get_dentry(struct super_block *sb,
 				     struct ovl_path *lowerpath,
 				     struct dentry *index)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 	const struct ovl_layer *layer = upper ? &ofs->layers[0] : lowerpath->layer;
 	struct dentry *real = upper ?: (index ?: lowerpath->dentry);
 
@@ -680,7 +680,7 @@ static struct dentry *ovl_get_dentry(struct super_block *sb,
 static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
 					struct ovl_fh *fh)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 	struct dentry *dentry;
 	struct dentry *upper;
 
@@ -700,7 +700,7 @@ static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
 static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
 					struct ovl_fh *fh)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 	struct ovl_path origin = { };
 	struct ovl_path *stack = &origin;
 	struct dentry *dentry = NULL;
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 541cf3717fc2..c27823f6e7aa 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -334,7 +334,7 @@ static const char *ovl_get_link(struct dentry *dentry,
 
 bool ovl_is_private_xattr(struct super_block *sb, const char *name)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 
 	if (ofs->config.userxattr)
 		return strncmp(name, OVL_XATTR_USER_PREFIX,
@@ -689,7 +689,7 @@ int ovl_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
 int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags)
 {
 	if (flags & S_ATIME) {
-		struct ovl_fs *ofs = inode->i_sb->s_fs_info;
+		struct ovl_fs *ofs = OVL_FS(inode->i_sb);
 		struct path upperpath = {
 			.mnt = ovl_upper_mnt(ofs),
 			.dentry = ovl_upperdentry_dereference(OVL_I(inode)),
@@ -952,7 +952,7 @@ static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode)
 
 static void ovl_next_ino(struct inode *inode)
 {
-	struct ovl_fs *ofs = inode->i_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(inode->i_sb);
 
 	inode->i_ino = atomic_long_inc_return(&ofs->last_ino);
 	if (unlikely(!inode->i_ino))
@@ -1284,7 +1284,7 @@ struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir)
 static bool ovl_hash_bylower(struct super_block *sb, struct dentry *upper,
 			     struct dentry *lower, bool index)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 
 	/* No, if pure upper */
 	if (!lower)
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index cfb3420b7df0..d0f196b85541 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -832,7 +832,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 {
 	struct ovl_entry *oe;
 	const struct cred *old_cred;
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	struct ovl_entry *poe = dentry->d_parent->d_fsdata;
 	struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
 	struct ovl_path *stack = NULL, *origin_path = NULL;
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index fd11fe6d6d45..b91b3694ae26 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -5,6 +5,8 @@
  * Copyright (C) 2016 Red Hat, Inc.
  */
 
+#include <uapi/linux/magic.h>
+
 struct ovl_config {
 	char *lowerdir;
 	char *upperdir;
@@ -97,6 +99,8 @@ static inline struct mnt_idmap *ovl_upper_mnt_idmap(struct ovl_fs *ofs)
 
 static inline struct ovl_fs *OVL_FS(struct super_block *sb)
 {
+	/* Make sure OVL_FS() is always used with an overlayfs superblock */
+	BUG_ON(sb->s_magic != OVERLAYFS_SUPER_MAGIC);
 	return (struct ovl_fs *)sb->s_fs_info;
 }
 
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index f97ad8b40dbb..879d601ba61e 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -259,7 +259,7 @@ static void ovl_free_fs(struct ovl_fs *ofs)
 
 static void ovl_put_super(struct super_block *sb)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 
 	ovl_free_fs(ofs);
 }
@@ -267,7 +267,7 @@ static void ovl_put_super(struct super_block *sb)
 /* Sync real dirty inodes in upper filesystem (if it exists) */
 static int ovl_sync_fs(struct super_block *sb, int wait)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 	struct super_block *upper_sb;
 	int ret;
 
@@ -315,7 +315,7 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
  */
 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	struct dentry *root_dentry = dentry->d_sb->s_root;
 	struct path path;
 	int err;
@@ -364,7 +364,7 @@ static inline int ovl_xino_def(void)
 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 {
 	struct super_block *sb = dentry->d_sb;
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 
 	seq_show_option(m, "lowerdir", ofs->config.lowerdir);
 	if (ofs->config.upperdir) {
@@ -396,7 +396,7 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 
 static int ovl_remount(struct super_block *sb, int *flags, char *data)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 	struct super_block *upper_sb;
 	int ret = 0;
 
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 923d66d131c1..2425240ef139 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -18,25 +18,25 @@
 
 int ovl_want_write(struct dentry *dentry)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	return mnt_want_write(ovl_upper_mnt(ofs));
 }
 
 void ovl_drop_write(struct dentry *dentry)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	mnt_drop_write(ovl_upper_mnt(ofs));
 }
 
 struct dentry *ovl_workdir(struct dentry *dentry)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	return ofs->workdir;
 }
 
 const struct cred *ovl_override_creds(struct super_block *sb)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 
 	return override_creds(ofs->creator_cred);
 }
@@ -62,7 +62,7 @@ int ovl_can_decode_fh(struct super_block *sb)
 
 struct dentry *ovl_indexdir(struct super_block *sb)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 
 	return ofs->indexdir;
 }
@@ -70,7 +70,7 @@ struct dentry *ovl_indexdir(struct super_block *sb)
 /* Index all files on copy up. For now only enabled for NFS export */
 bool ovl_index_all(struct super_block *sb)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 
 	return ofs->config.nfs_export && ofs->config.index;
 }
@@ -78,7 +78,7 @@ bool ovl_index_all(struct super_block *sb)
 /* Verify lower origin on lookup. For now only enabled for NFS export */
 bool ovl_verify_lower(struct super_block *sb)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 
 	return ofs->config.nfs_export && ofs->config.index;
 }
@@ -152,7 +152,7 @@ enum ovl_path_type ovl_path_type(struct dentry *dentry)
 
 void ovl_path_upper(struct dentry *dentry, struct path *path)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 
 	path->mnt = ovl_upper_mnt(ofs);
 	path->dentry = ovl_dentry_upper(dentry);
@@ -415,7 +415,7 @@ bool ovl_dentry_needs_data_copy_up(struct dentry *dentry, int flags)
 
 bool ovl_redirect_dir(struct super_block *sb)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 
 	return ofs->config.redirect_dir && !ofs->noxattr;
 }
-- 
2.39.2