[PATCH stable/linux-5.10.y 1/7] ovl: pass layer mnt to ovl_open_realfile()

[Cai Xinchen]

From: Amir Goldstein <amir73il at gmail.com>

[ Upstream commit 1248ea4b91bcdafefdb025087e67d58382cfc9eb ]

Ensure that ovl_open_realfile() takes the mount's idmapping into
account. We add a new helper ovl_path_realdata() that can be used to
easily retrieve the relevant path which we can pass down. This is needed
to support idmapped base layers with overlay.

Cc: <linux-unionfs at vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan at redhat.com>
Reviewed-by: Christian Brauner (Microsoft) <brauner at kernel.org>
Signed-off-by: Amir Goldstein <amir73il at gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner at kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi at redhat.com>
Signed-off-by: Cai Xinchen <caixinchen1 at huawei.com>
---
 fs/overlayfs/file.c      | 22 +++++++++++++---------
 fs/overlayfs/overlayfs.h |  1 +
 fs/overlayfs/util.c      | 14 ++++++++++++++
 3 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 4440ff43cb66..343db8b3ecd6 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -37,8 +37,9 @@ static char ovl_whatisit(struct inode *inode, struct inode *realinode)
 #define OVL_OPEN_FLAGS (O_NOATIME | FMODE_NONOTIFY)
 
 static struct file *ovl_open_realfile(const struct file *file,
-				      struct inode *realinode)
+				      struct path *realpath)
 {
+	struct inode *realinode = d_inode(realpath->dentry);
 	struct inode *inode = file_inode(file);
 	struct file *realfile;
 	const struct cred *old_cred;
@@ -103,21 +104,21 @@ static int ovl_change_flags(struct file *file, unsigned int flags)
 static int ovl_real_fdget_meta(const struct file *file, struct fd *real,
 			       bool allow_meta)
 {
-	struct inode *inode = file_inode(file);
-	struct inode *realinode;
+	struct dentry *dentry = file_dentry(file);
+	struct path realpath;
 
 	real->flags = 0;
 	real->file = file->private_data;
 
 	if (allow_meta)
-		realinode = ovl_inode_real(inode);
+		ovl_path_real(dentry, &realpath);
 	else
-		realinode = ovl_inode_realdata(inode);
+		ovl_path_realdata(dentry, &realpath);
 
 	/* Has it been copied up since we'd opened it? */
-	if (unlikely(file_inode(real->file) != realinode)) {
+	if (unlikely(file_inode(real->file) != d_inode(realpath.dentry))) {
 		real->flags = FDPUT_FPUT;
-		real->file = ovl_open_realfile(file, realinode);
+		real->file = ovl_open_realfile(file, &realpath);
 
 		return PTR_ERR_OR_ZERO(real->file);
 	}
@@ -143,17 +144,20 @@ static int ovl_real_fdget(const struct file *file, struct fd *real)
 
 static int ovl_open(struct inode *inode, struct file *file)
 {
+	struct dentry *dentry = file_dentry(file);
 	struct file *realfile;
+	struct path realpath;
 	int err;
 
-	err = ovl_maybe_copy_up(file_dentry(file), file->f_flags);
+	err = ovl_maybe_copy_up(dentry, file->f_flags);
 	if (err)
 		return err;
 
 	/* No longer need these flags, so don't pass them on to underlying fs */
 	file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 
-	realfile = ovl_open_realfile(file, ovl_inode_realdata(inode));
+	ovl_path_realdata(dentry, &realpath);
+	realfile = ovl_open_realfile(file, &realpath);
 	if (IS_ERR(realfile))
 		return PTR_ERR(realfile);
 
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 5ac968f709a4..5b8a1c9bc355 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -274,6 +274,7 @@ void ovl_path_upper(struct dentry *dentry, struct path *path);
 void ovl_path_lower(struct dentry *dentry, struct path *path);
 void ovl_path_lowerdata(struct dentry *dentry, struct path *path);
 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path);
+enum ovl_path_type ovl_path_realdata(struct dentry *dentry, struct path *path);
 struct dentry *ovl_dentry_upper(struct dentry *dentry);
 struct dentry *ovl_dentry_lower(struct dentry *dentry);
 struct dentry *ovl_dentry_lowerdata(struct dentry *dentry);
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 26f29a3e5ada..431dfe3db0cc 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -209,6 +209,20 @@ enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
 	return type;
 }
 
+enum ovl_path_type ovl_path_realdata(struct dentry *dentry, struct path *path)
+{
+	enum ovl_path_type type = ovl_path_type(dentry);
+
+	WARN_ON_ONCE(d_is_dir(dentry));
+
+	if (!OVL_TYPE_UPPER(type) || OVL_TYPE_MERGE(type))
+		ovl_path_lowerdata(dentry, path);
+	else
+		ovl_path_upper(dentry, path);
+
+	return type;
+}
+
 struct dentry *ovl_dentry_upper(struct dentry *dentry)
 {
 	struct inode *inode = d_inode(dentry);
-- 
2.18.0.huawei.25