[PATCH v5 15/19] ovl: use ovl_copy_{real,upper}attr() wrappers

[Christian Brauner <brauner@kernel.org>]

When copying inode attributes we from the upper or lower layer to ovl
inodes we need to take the upper or lower layer's mount's idmapping into
account. In a lot of places we call ovl_copyattr() only on upper inodes
and in some we call it on either upper or lower inodes. Split this into
two separate helpers.

The first one should only be called on upper
inodes and is thus called ovl_copy_upperattr(). The second one can be
called on upper or lower inodes. We add ovl_copy_realattr() for this
task. The new helper makes use of the previously added ovl_i_path_real()
helper. This is needed to support idmapped base layers with overlay.

When overlay copies the inode information from an upper or lower layer
to the relevant overlay inode it will apply the idmapping of the upper
or lower layer when doing so. The ovl inode ownership will thus always
correctly reflect the ownership of the idmapped upper or lower layer.

All idmapping helpers are nops when no idmapped base layers are used.

Cc: <linux-unionfs@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
---
/* v2 */
unchanged

/* v3 */
unchanged

/* v4 */
- Vivek Goyal <vgoyal@redhat.com>:
  - rename some variables

/* v5 */
unchanged
---
 fs/overlayfs/dir.c       |  6 +++---
 fs/overlayfs/file.c      | 15 +++++++--------
 fs/overlayfs/inode.c     |  8 ++++----
 fs/overlayfs/overlayfs.h | 22 +++++++++++++---------
 fs/overlayfs/util.c      | 27 ++++++++++++++++++++++++++-
 5 files changed, 53 insertions(+), 25 deletions(-)

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 4ab62e9b2b7a..381c7fa10ae1 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -930,7 +930,7 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 	 */
 	upperdentry = ovl_dentry_upper(dentry);
 	if (upperdentry)
-		ovl_copyattr(d_inode(upperdentry), d_inode(dentry));
+		ovl_copy_upperattr(d_inode(upperdentry), d_inode(dentry));
 
 out_drop_write:
 	ovl_drop_write(dentry);
@@ -1278,9 +1278,9 @@ static int ovl_rename(struct user_namespace *mnt_userns, struct inode *olddir,
 			 (d_inode(new) && ovl_type_origin(new)));
 
 	/* copy ctime: */
-	ovl_copyattr(d_inode(olddentry), d_inode(old));
+	ovl_copy_upperattr(d_inode(olddentry), d_inode(old));
 	if (d_inode(new) && ovl_dentry_upper(new))
-		ovl_copyattr(d_inode(newdentry), d_inode(new));
+		ovl_copy_upperattr(d_inode(newdentry), d_inode(new));
 
 out_dput:
 	dput(newdentry);
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 9250e04e97af..656c30bf20a6 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -277,7 +277,7 @@ static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
 		__sb_writers_acquired(file_inode(iocb->ki_filp)->i_sb,
 				      SB_FREEZE_WRITE);
 		file_end_write(iocb->ki_filp);
-		ovl_copyattr(ovl_inode_real(inode), inode);
+		ovl_copy_realattr(inode);
 	}
 
 	orig_iocb->ki_pos = iocb->ki_pos;
@@ -360,7 +360,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 
 	inode_lock(inode);
 	/* Update mode */
-	ovl_copyattr(ovl_inode_real(inode), inode);
+	ovl_copy_realattr(inode);
 	ret = file_remove_privs(file);
 	if (ret)
 		goto out_unlock;
@@ -385,7 +385,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 				     ovl_iocb_to_rwf(ifl));
 		file_end_write(real.file);
 		/* Update size */
-		ovl_copyattr(ovl_inode_real(inode), inode);
+		ovl_copy_realattr(inode);
 	} else {
 		struct ovl_aio_req *aio_req;
 
@@ -435,12 +435,11 @@ static ssize_t ovl_splice_write(struct pipe_inode_info *pipe, struct file *out,
 	struct fd real;
 	const struct cred *old_cred;
 	struct inode *inode = file_inode(out);
-	struct inode *realinode = ovl_inode_real(inode);
 	ssize_t ret;
 
 	inode_lock(inode);
 	/* Update mode */
-	ovl_copyattr(realinode, inode);
+	ovl_copy_realattr(inode);
 	ret = file_remove_privs(out);
 	if (ret)
 		goto out_unlock;
@@ -456,7 +455,7 @@ static ssize_t ovl_splice_write(struct pipe_inode_info *pipe, struct file *out,
 
 	file_end_write(real.file);
 	/* Update size */
-	ovl_copyattr(realinode, inode);
+	ovl_copy_realattr(inode);
 	revert_creds(old_cred);
 	fdput(real);
 
@@ -530,7 +529,7 @@ static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len
 	revert_creds(old_cred);
 
 	/* Update size */
-	ovl_copyattr(ovl_inode_real(inode), inode);
+	ovl_copy_realattr(inode);
 
 	fdput(real);
 
@@ -602,7 +601,7 @@ static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
 	revert_creds(old_cred);
 
 	/* Update size */
-	ovl_copyattr(ovl_inode_real(inode_out), inode_out);
+	ovl_copy_realattr(inode_out);
 
 	fdput(real_in);
 	fdput(real_out);
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index e28b7ed755b3..44fa578267fa 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -81,7 +81,7 @@ int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 		err = ovl_do_notify_change(ofs, upperdentry, attr);
 		revert_creds(old_cred);
 		if (!err)
-			ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
+			ovl_copy_upperattr(upperdentry->d_inode, dentry->d_inode);
 		inode_unlock(upperdentry->d_inode);
 
 		if (winode)
@@ -379,7 +379,7 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
 	revert_creds(old_cred);
 
 	/* copy c/mtime */
-	ovl_copyattr(d_inode(realdentry), inode);
+	ovl_copy_upperattr(d_inode(realdentry), inode);
 
 out_drop_write:
 	ovl_drop_write(dentry);
@@ -581,7 +581,7 @@ int ovl_fileattr_set(struct user_namespace *mnt_userns,
 		inode_set_flags(inode, flags, OVL_COPY_I_FLAGS_MASK);
 
 		/* Update ctime */
-		ovl_copyattr(ovl_inode_real(inode), inode);
+		ovl_copy_realattr(inode);
 	}
 	ovl_drop_write(dentry);
 out:
@@ -791,7 +791,7 @@ void ovl_inode_init(struct inode *inode, struct ovl_inode_params *oip,
 		oi->lowerdata = igrab(d_inode(oip->lowerdata));
 
 	realinode = ovl_inode_real(inode);
-	ovl_copyattr(realinode, inode);
+	ovl_copy_realattr(inode);
 	ovl_copyflags(realinode, inode);
 	ovl_map_ino(inode, ino, fsid);
 }
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 965588106e00..a49950a1a651 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -619,15 +619,19 @@ bool ovl_lookup_trap_inode(struct super_block *sb, struct dentry *dir);
 struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir);
 struct inode *ovl_get_inode(struct super_block *sb,
 			    struct ovl_inode_params *oip);
-static inline void ovl_copyattr(struct inode *from, struct inode *to)
-{
-	to->i_uid = from->i_uid;
-	to->i_gid = from->i_gid;
-	to->i_mode = from->i_mode;
-	to->i_atime = from->i_atime;
-	to->i_mtime = from->i_mtime;
-	to->i_ctime = from->i_ctime;
-	i_size_write(to, i_size_read(from));
+void ovl_do_copyattr(struct vfsmount *realmnt, struct inode *realinode,
+		     struct inode *inode);
+static inline void ovl_copy_upperattr(struct inode *upperinode, struct inode *to)
+{
+	ovl_do_copyattr(ovl_upper_mnt(OVL_FS(to->i_sb)), upperinode, to);
+}
+
+static inline void ovl_copy_realattr(struct inode *to)
+{
+	struct path realpath;
+
+	ovl_i_path_real(to, &realpath);
+	ovl_do_copyattr(realpath.mnt, d_inode(realpath.dentry), to);
 }
 
 /* vfs inode flags copied from real to ovl inode */
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 7dd9901c9d17..90182d9d7735 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -500,7 +500,7 @@ static void ovl_dir_version_inc(struct dentry *dentry, bool impurity)
 void ovl_dir_modified(struct dentry *dentry, bool impurity)
 {
 	/* Copy mtime/ctime */
-	ovl_copyattr(d_inode(ovl_dentry_upper(dentry)), d_inode(dentry));
+	ovl_copy_upperattr(d_inode(ovl_dentry_upper(dentry)), d_inode(dentry));
 
 	ovl_dir_version_inc(dentry, impurity);
 }
@@ -1116,3 +1116,28 @@ int ovl_sync_status(struct ovl_fs *ofs)
 
 	return errseq_check(&mnt->mnt_sb->s_wb_err, ofs->errseq);
 }
+
+/*
+ * ovl_do_copyattr() - copy inode attributes from layer to ovl inode
+ *
+ * When overlay copies inode information from an upper or lower layer to the
+ * relevant overlay inode it will apply the idmapping of the upper or lower
+ * layer when doing so ensuring that the ovl inode ownership will correctly
+ * reflect the ownership of the idmapped upper or lower layer. For example, an
+ * idmapped upper or lower layer mapping id 1001 to id 1000 will take care to
+ * map any lower or upper inode owned by id 1001 to id 1000. These mapping
+ * helpers are nops when the relevant layer isn't idmapped.
+ */
+void ovl_do_copyattr(struct vfsmount *realmnt, struct inode *realinode,
+		     struct inode *inode)
+{
+	struct user_namespace *real_mnt_userns = mnt_user_ns(realmnt);
+
+	inode->i_uid = i_uid_into_mnt(real_mnt_userns, realinode);
+	inode->i_gid = i_gid_into_mnt(real_mnt_userns, realinode);
+	inode->i_mode = realinode->i_mode;
+	inode->i_atime = realinode->i_atime;
+	inode->i_mtime = realinode->i_mtime;
+	inode->i_ctime = realinode->i_ctime;
+	i_size_write(inode, i_size_read(realinode));
+}
-- 
2.32.0