fs: port i_{g,u}id_into_vfs{g,u}id() to mnt_idmap

Convert to struct mnt_idmap.
Remove legacy file_mnt_user_ns() and mnt_user_ns().

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

1 files changed, 8 insertions, 16 deletions

diff --git a/fs/attr.c b/fs/attr.c
index bbb9118c6c8b..a627ac74c4b1 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -36,15 +36,13 @@
 int setattr_should_drop_sgid(struct mnt_idmap *idmap,
 			     const struct inode *inode)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	umode_t mode = inode->i_mode;
 
 	if (!(mode & S_ISGID))
 		return 0;
 	if (mode & S_IXGRP)
 		return ATTR_KILL_SGID;
-	if (!in_group_or_capable(idmap, inode,
-				 i_gid_into_vfsgid(mnt_userns, inode)))
+	if (!in_group_or_capable(idmap, inode, i_gid_into_vfsgid(idmap, inode)))
 		return ATTR_KILL_SGID;
 	return 0;
 }
@@ -98,9 +96,7 @@ EXPORT_SYMBOL(setattr_should_drop_suidgid);
 static bool chown_ok(struct mnt_idmap *idmap,
 		     const struct inode *inode, vfsuid_t ia_vfsuid)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
-
-	vfsuid_t vfsuid = i_uid_into_vfsuid(mnt_userns, inode);
+	vfsuid_t vfsuid = i_uid_into_vfsuid(idmap, inode);
 	if (vfsuid_eq_kuid(vfsuid, current_fsuid()) &&
 	    vfsuid_eq(ia_vfsuid, vfsuid))
 		return true;
@@ -127,10 +123,8 @@ static bool chown_ok(struct mnt_idmap *idmap,
 static bool chgrp_ok(struct mnt_idmap *idmap,
 		     const struct inode *inode, vfsgid_t ia_vfsgid)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
-
-	vfsgid_t vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
-	vfsuid_t vfsuid = i_uid_into_vfsuid(mnt_userns, inode);
+	vfsgid_t vfsgid = i_gid_into_vfsgid(idmap, inode);
+	vfsuid_t vfsuid = i_uid_into_vfsuid(idmap, inode);
 	if (vfsuid_eq_kuid(vfsuid, current_fsuid())) {
 		if (vfsgid_eq(ia_vfsgid, vfsgid))
 			return true;
@@ -169,7 +163,6 @@ static bool chgrp_ok(struct mnt_idmap *idmap,
 int setattr_prepare(struct mnt_idmap *idmap, struct dentry *dentry,
 		    struct iattr *attr)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	struct inode *inode = d_inode(dentry);
 	unsigned int ia_valid = attr->ia_valid;
 
@@ -207,7 +200,7 @@ int setattr_prepare(struct mnt_idmap *idmap, struct dentry *dentry,
 		if (ia_valid & ATTR_GID)
 			vfsgid = attr->ia_vfsgid;
 		else
-			vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
+			vfsgid = i_gid_into_vfsgid(idmap, inode);
 
 		/* Also check the setgid bit! */
 		if (!in_group_or_capable(idmap, inode, vfsgid))
@@ -308,7 +301,6 @@ EXPORT_SYMBOL(inode_newsize_ok);
 void setattr_copy(struct mnt_idmap *idmap, struct inode *inode,
 		  const struct iattr *attr)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	unsigned int ia_valid = attr->ia_valid;
 
 	i_uid_update(idmap, attr, inode);
@@ -322,7 +314,7 @@ void setattr_copy(struct mnt_idmap *idmap, struct inode *inode,
 	if (ia_valid & ATTR_MODE) {
 		umode_t mode = attr->ia_mode;
 		if (!in_group_or_capable(idmap, inode,
-					 i_gid_into_vfsgid(mnt_userns, inode)))
+					 i_gid_into_vfsgid(idmap, inode)))
 			mode &= ~S_ISGID;
 		inode->i_mode = mode;
 	}
@@ -473,10 +465,10 @@ int notify_change(struct mnt_idmap *idmap, struct dentry *dentry,
 	 * gids unless those uids & gids are being made valid.
 	 */
 	if (!(ia_valid & ATTR_UID) &&
-	    !vfsuid_valid(i_uid_into_vfsuid(mnt_userns, inode)))
+	    !vfsuid_valid(i_uid_into_vfsuid(idmap, inode)))
 		return -EOVERFLOW;
 	if (!(ia_valid & ATTR_GID) &&
-	    !vfsgid_valid(i_gid_into_vfsgid(mnt_userns, inode)))
+	    !vfsgid_valid(i_gid_into_vfsgid(idmap, inode)))
 		return -EOVERFLOW;
 
 	error = security_inode_setattr(idmap, dentry, attr);