fs: port xattr to mnt_idmap

Convert to struct mnt_idmap.

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, 5 insertions, 4 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index a32a814a694d..706bb440f837 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3145,7 +3145,7 @@ static bool has_cap_mac_admin(bool audit)
 	return true;
 }
 
-static int selinux_inode_setxattr(struct user_namespace *mnt_userns,
+static int selinux_inode_setxattr(struct mnt_idmap *idmap,
 				  struct dentry *dentry, const char *name,
 				  const void *value, size_t size, int flags)
 {
@@ -3154,6 +3154,7 @@ static int selinux_inode_setxattr(struct user_namespace *mnt_userns,
 	struct superblock_security_struct *sbsec;
 	struct common_audit_data ad;
 	u32 newsid, sid = current_sid();
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	int rc = 0;
 
 	if (strcmp(name, XATTR_NAME_SELINUX)) {
@@ -3313,11 +3314,11 @@ static int selinux_inode_listxattr(struct dentry *dentry)
 	return dentry_has_perm(cred, dentry, FILE__GETATTR);
 }
 
-static int selinux_inode_removexattr(struct user_namespace *mnt_userns,
+static int selinux_inode_removexattr(struct mnt_idmap *idmap,
 				     struct dentry *dentry, const char *name)
 {
 	if (strcmp(name, XATTR_NAME_SELINUX)) {
-		int rc = cap_inode_removexattr(mnt_userns, dentry, name);
+		int rc = cap_inode_removexattr(idmap, dentry, name);
 		if (rc)
 			return rc;
 
@@ -6588,7 +6589,7 @@ static int selinux_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen
  */
 static int selinux_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen)
 {
-	return __vfs_setxattr_noperm(&init_user_ns, dentry, XATTR_NAME_SELINUX,
+	return __vfs_setxattr_noperm(&nop_mnt_idmap, dentry, XATTR_NAME_SELINUX,
 				     ctx, ctxlen, 0);
 }