From: Al Viro <viro@zeniv.linux.org.uk>
Date: Tue, 26 Aug 2025 21:12:15 +0000 (-0400)
Subject: copy_mnt_ns(): use guards
X-Git-Tag: v6.18-rc1~128^2~6
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=d7b7253a0adc6e24869ef74a2085767cb11eb6fc;p=thirdparty%2Flinux.git

copy_mnt_ns(): use guards

* mntput() of rootmnt and pwdmnt done via __free(mntput)
* mnt_ns_tree_add() can be done within namespace_excl scope.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/namespace.c b/fs/namespace.c
index b4374d6d4bae2..b5a082fae0066 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4158,7 +4158,8 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
 		struct user_namespace *user_ns, struct fs_struct *new_fs)
 {
 	struct mnt_namespace *new_ns;
-	struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
+	struct vfsmount *rootmnt __free(mntput) = NULL;
+	struct vfsmount *pwdmnt __free(mntput) = NULL;
 	struct mount *p, *q;
 	struct mount *old;
 	struct mount *new;
@@ -4177,7 +4178,7 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
 	if (IS_ERR(new_ns))
 		return new_ns;
 
-	namespace_lock();
+	guard(namespace_excl)();
 	/* First pass: copy the tree topology */
 	copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
 	if (user_ns != ns->user_ns)
@@ -4185,13 +4186,11 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
 	new = copy_tree(old, old->mnt.mnt_root, copy_flags);
 	if (IS_ERR(new)) {
 		emptied_ns = new_ns;
-		namespace_unlock();
 		return ERR_CAST(new);
 	}
 	if (user_ns != ns->user_ns) {
-		lock_mount_hash();
+		guard(mount_writer)();
 		lock_mnt_tree(new);
-		unlock_mount_hash();
 	}
 	new_ns->root = new;
 
@@ -4223,13 +4222,6 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
 		while (p->mnt.mnt_root != q->mnt.mnt_root)
 			p = next_mnt(skip_mnt_tree(p), old);
 	}
-	namespace_unlock();
-
-	if (rootmnt)
-		mntput(rootmnt);
-	if (pwdmnt)
-		mntput(pwdmnt);
-
 	mnt_ns_tree_add(new_ns);
 	return new_ns;
 }