Introduce ovl_do_notify_change() as a simple wrapper around
notify_change() to support idmapped layers. The helper mirrors other
ovl_do_*() helpers that operate on the upper layers.
When changing ownership of an upper object the intended ownership needs
to be mapped according to the upper layer's idmapping. This mapping is
the inverse to the mapping applied when copying inode information from
an upper layer to the corresponding overlay inode. So e.g., when an
upper mount maps files that are stored on-disk as owned by id 1001 to
1000 this means that calling stat on this object from an idmapped mount
will report the file as being owned by id 1000. Consequently in order to
change ownership of an object in this filesystem so it appears as being
owned by id 1000 in the upper idmapped layer it needs to store id 1001
on disk. The mnt mapping helpers take care of this.
All idmapping helpers are nops when no idmapped base layers are used.
Cc: <linux-unionfs@xxxxxxxxxxxxxxx>
Tested-by: Giuseppe Scrivano <gscrivan@xxxxxxxxxx>
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
Signed-off-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx>
---
fs/overlayfs/copy_up.c | 8 ++++----
fs/overlayfs/dir.c | 2 +-
fs/overlayfs/inode.c | 3 ++-
fs/overlayfs/overlayfs.h | 25 +++++++++++++++++++++++++
fs/overlayfs/ovl_entry.h | 5 +++++
fs/overlayfs/super.c | 2 +-
6 files changed, 38 insertions(+), 7 deletions(-)
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 2c336acb2ba0..a5d68302693f 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -301,7 +301,7 @@ static int ovl_set_size(struct ovl_fs *ofs,
.ia_size = stat->size,
};
- return notify_change(&init_user_ns, upperdentry, &attr, NULL);
+ return ovl_do_notify_change(ofs, upperdentry, &attr);
}
static int ovl_set_timestamps(struct ovl_fs *ofs, struct dentry *upperdentry,
@@ -314,7 +314,7 @@ static int ovl_set_timestamps(struct ovl_fs *ofs, struct dentry *upperdentry,
.ia_mtime = stat->mtime,
};
- return notify_change(&init_user_ns, upperdentry, &attr, NULL);
+ return ovl_do_notify_change(ofs, upperdentry, &attr);
}
int ovl_set_attr(struct ovl_fs *ofs, struct dentry *upperdentry,
@@ -327,7 +327,7 @@ int ovl_set_attr(struct ovl_fs *ofs, struct dentry *upperdentry,
.ia_valid = ATTR_MODE,
.ia_mode = stat->mode,
};
- err = notify_change(&init_user_ns, upperdentry, &attr, NULL);
+ err = ovl_do_notify_change(ofs, upperdentry, &attr);
}
if (!err) {
struct iattr attr = {
@@ -335,7 +335,7 @@ int ovl_set_attr(struct ovl_fs *ofs, struct dentry *upperdentry,
.ia_uid = stat->uid,
.ia_gid = stat->gid,
};
- err = notify_change(&init_user_ns, upperdentry, &attr, NULL);
+ err = ovl_do_notify_change(ofs, upperdentry, &attr);
}
if (!err)
ovl_set_timestamps(ofs, upperdentry, stat);
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 27a40b6754f4..9ae0352ff52a 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -516,7 +516,7 @@ static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
.ia_mode = cattr->mode,
};
inode_lock(newdentry->d_inode);
- err = notify_change(&init_user_ns, newdentry, &attr, NULL);
+ err = ovl_do_notify_change(ofs, newdentry, &attr);
inode_unlock(newdentry->d_inode);
if (err)
goto out_cleanup;
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index c51a9dd36cc7..9a8e6b94d9e8 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -21,6 +21,7 @@ int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
struct iattr *attr)
{
int err;
+ struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
bool full_copy_up = false;
struct dentry *upperdentry;
const struct cred *old_cred;
@@ -77,7 +78,7 @@ int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
inode_lock(upperdentry->d_inode);
old_cred = ovl_override_creds(dentry->d_sb);
- err = notify_change(&init_user_ns, upperdentry, attr, NULL);
+ err = ovl_do_notify_change(ofs, upperdentry, attr);
revert_creds(old_cred);
if (!err)
ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 816a69b46b67..eff8a1edb693 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -122,6 +122,31 @@ static inline const char *ovl_xattr(struct ovl_fs *ofs, enum ovl_xattr ox)
return ovl_xattr_table[ox][ofs->config.userxattr];
}
+/*
+ * When changing ownership of an upper object map the intended ownership
+ * according to the upper layer's idmapping. When an upper mount idmaps files
+ * that are stored on-disk as owned by id 1001 to id 1000 this means stat on
+ * this object will report it as being owned by id 1000 when calling via the
+ * upper mount. So in order to change ownership of an object so it reports id
+ * 1000 when calling stat on it through the upper mount the value written to
+ * disk must be 1001. The mount mapping helper will take of this. The mnt
+ * idmapping helpers are nops if the upper layer isn't idmapped.
+ */
+static inline int ovl_do_notify_change(struct ovl_fs *ofs,
+ struct dentry *upperdentry,
+ struct iattr *attr)
+{
+ struct user_namespace *upper_idmap = ovl_upper_idmap(ofs);
+ struct user_namespace *fs_idmap = i_user_ns(d_inode(upperdentry));
+
+ if (attr->ia_valid & ATTR_UID)
+ attr->ia_uid = mapped_kuid_user(upper_idmap, fs_idmap, attr->ia_uid);
+ if (attr->ia_valid & ATTR_GID)
+ attr->ia_gid = mapped_kgid_user(upper_idmap, fs_idmap, attr->ia_gid);
+
+ return notify_change(ovl_upper_idmap(ofs), upperdentry, attr, NULL);
+}
+
static inline int ovl_do_rmdir(struct ovl_fs *ofs,
struct inode *dir, struct dentry *dentry)
{
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 63efee554f69..cf6aebcf893c 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -90,6 +90,11 @@ static inline struct vfsmount *ovl_upper_mnt(struct ovl_fs *ofs)
return ofs->layers[0].mnt;
}
+static inline struct user_namespace *ovl_upper_idmap(struct ovl_fs *ofs)
+{
+ return mnt_user_ns(ovl_upper_mnt(ofs));
+}
+
static inline struct ovl_fs *OVL_FS(struct super_block *sb)
{
return (struct ovl_fs *)sb->s_fs_info;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index f1deb84aebcf..2cc27e707cb3 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -821,7 +821,7 @@ static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
/* Clear any inherited mode bits */
inode_lock(work->d_inode);
- err = notify_change(&init_user_ns, work, &attr, NULL);
+ err = ovl_do_notify_change(ofs, work, &attr);
inode_unlock(work->d_inode);
if (err)
goto out_dput;
--
2.32.0
