ovl: do operations on underlying file system in mounter's context

Given we are now doing checks both on overlay inode as well underlying
inode, we should be able to do checks and operations on underlying file
system using mounter's context.

So modify all operations to do checks/operations on underlying dentry/inode
in the context of mounter.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 29 insertions, 31 deletions

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index aa63205571967..7195306e9f843 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -138,9 +138,12 @@ static int ovl_dir_getattr(struct vfsmount *mnt, struct dentry *dentry,
 	int err;
 	enum ovl_path_type type;
 	struct path realpath;
+	const struct cred *old_cred;
 
 	type = ovl_path_real(dentry, &realpath);
+	old_cred = ovl_override_creds(dentry->d_sb);
 	err = vfs_getattr(&realpath, stat);
+	revert_creds(old_cred);
 	if (err)
 		return err;
 
@@ -391,6 +394,8 @@ static int ovl_create_or_link(struct dentry *dentry, int mode, dev_t rdev,
 {
 	int err;
 	struct inode *inode;
+	const struct cred *old_cred;
+	struct cred *override_cred;
 	struct kstat stat = {
 		.mode = mode,
 		.rdev = rdev,
@@ -405,28 +410,23 @@ static int ovl_create_or_link(struct dentry *dentry, int mode, dev_t rdev,
 	if (err)
 		goto out_iput;
 
-	if (!ovl_dentry_is_opaque(dentry)) {
-		err = ovl_create_upper(dentry, inode, &stat, link, hardlink);
-	} else {
-		const struct cred *old_cred;
-		struct cred *override_cred;
-
-		old_cred = ovl_override_creds(dentry->d_sb);
-
-		err = -ENOMEM;
-		override_cred = prepare_creds();
-		if (override_cred) {
-			override_cred->fsuid = old_cred->fsuid;
-			override_cred->fsgid = old_cred->fsgid;
-			put_cred(override_creds(override_cred));
-			put_cred(override_cred);
-
+	old_cred = ovl_override_creds(dentry->d_sb);
+	err = -ENOMEM;
+	override_cred = prepare_creds();
+	if (override_cred) {
+		override_cred->fsuid = old_cred->fsuid;
+		override_cred->fsgid = old_cred->fsgid;
+		put_cred(override_creds(override_cred));
+		put_cred(override_cred);
+
+		if (!ovl_dentry_is_opaque(dentry))
+			err = ovl_create_upper(dentry, inode, &stat, link,
+						hardlink);
+		else
 			err = ovl_create_over_whiteout(dentry, inode, &stat,
-						       link, hardlink);
-		}
-		revert_creds(old_cred);
+							link, hardlink);
 	}
-
+	revert_creds(old_cred);
 	if (!err)
 		inode = NULL;
 out_iput:
@@ -637,6 +637,8 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 {
 	enum ovl_path_type type;
 	int err;
+	const struct cred *old_cred;
+
 
 	err = ovl_check_sticky(dentry);
 	if (err)
@@ -651,15 +653,13 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 		goto out_drop_write;
 
 	type = ovl_path_type(dentry);
-	if (OVL_TYPE_PURE_UPPER(type)) {
-		err = ovl_remove_upper(dentry, is_dir);
-	} else {
-		const struct cred *old_cred = ovl_override_creds(dentry->d_sb);
 
+	old_cred = ovl_override_creds(dentry->d_sb);
+	if (OVL_TYPE_PURE_UPPER(type))
+		err = ovl_remove_upper(dentry, is_dir);
+	else
 		err = ovl_remove_and_whiteout(dentry, is_dir);
-
-		revert_creds(old_cred);
-	}
+	revert_creds(old_cred);
 out_drop_write:
 	ovl_drop_write(dentry);
 out:
@@ -764,8 +764,7 @@ static int ovl_rename2(struct inode *olddir, struct dentry *old,
 	old_opaque = !OVL_TYPE_PURE_UPPER(old_type);
 	new_opaque = !OVL_TYPE_PURE_UPPER(new_type);
 
-	if (old_opaque || new_opaque)
-		old_cred = ovl_override_creds(old->d_sb);
+	old_cred = ovl_override_creds(old->d_sb);
 
 	if (overwrite && OVL_TYPE_MERGE_OR_LOWER(new_type) && new_is_dir) {
 		opaquedir = ovl_check_empty_and_clear(new);
@@ -895,8 +894,7 @@ out_dput_old:
 out_unlock:
 	unlock_rename(new_upperdir, old_upperdir);
 out_revert_creds:
-	if (old_opaque || new_opaque)
-		revert_creds(old_cred);
+	revert_creds(old_cred);
 out_drop_write:
 	ovl_drop_write(old);
 out: