fs: make helpers idmap mount aware

Extend some inode methods with an additional user namespace argument. A
filesystem that is aware of idmapped mounts will receive the user
namespace the mount has been marked with. This can be used for
additional permission checking and also to enable filesystems to
translate between uids and gids if they need to. We have implemented all
relevant helpers in earlier patches.

As requested we simply extend the exisiting inode method instead of
introducing new ones. This is a little more code churn but it's mostly
mechanical and doesnt't leave us with additional inode methods.

Link: https://lore.kernel.org/r/20210121131959.646623-25-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

1 files changed, 32 insertions, 23 deletions

diff --git a/fs/namei.c b/fs/namei.c
index c8c083daf368..d9ceb75ac169 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -443,7 +443,7 @@ static inline int do_inode_permission(struct user_namespace *mnt_userns,
 {
 	if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
 		if (likely(inode->i_op->permission))
-			return inode->i_op->permission(inode, mask);
+			return inode->i_op->permission(mnt_userns, inode, mask);
 
 		/* This gets set once for the inode lifetime */
 		spin_lock(&inode->i_lock);
@@ -2199,11 +2199,13 @@ static int link_path_walk(const char *name, struct nameidata *nd)
 
 	/* At this point we know we have a real path component. */
 	for(;;) {
+		struct user_namespace *mnt_userns;
 		const char *link;
 		u64 hash_len;
 		int type;
 
-		err = may_lookup(&init_user_ns, nd);
+		mnt_userns = mnt_user_ns(nd->path.mnt);
+		err = may_lookup(mnt_userns, nd);
 		if (err)
 			return err;
 
@@ -2251,7 +2253,7 @@ static int link_path_walk(const char *name, struct nameidata *nd)
 OK:
 			/* pathname or trailing symlink, done */
 			if (!depth) {
-				nd->dir_uid = i_uid_into_mnt(&init_user_ns, nd->inode);
+				nd->dir_uid = i_uid_into_mnt(mnt_userns, nd->inode);
 				nd->dir_mode = nd->inode->i_mode;
 				nd->flags &= ~LOOKUP_PARENT;
 				return 0;
@@ -2904,7 +2906,7 @@ int vfs_create(struct user_namespace *mnt_userns, struct inode *dir,
 	error = security_inode_create(dir, dentry, mode);
 	if (error)
 		return error;
-	error = dir->i_op->create(dir, dentry, mode, want_excl);
+	error = dir->i_op->create(mnt_userns, dir, dentry, mode, want_excl);
 	if (!error)
 		fsnotify_create(dir, dentry);
 	return error;
@@ -2995,7 +2997,7 @@ static int may_open(struct user_namespace *mnt_userns, const struct path *path,
 	return 0;
 }
 
-static int handle_truncate(struct file *filp)
+static int handle_truncate(struct user_namespace *mnt_userns, struct file *filp)
 {
 	const struct path *path = &filp->f_path;
 	struct inode *inode = path->dentry->d_inode;
@@ -3009,7 +3011,7 @@ static int handle_truncate(struct file *filp)
 	if (!error)
 		error = security_path_truncate(path);
 	if (!error) {
-		error = do_truncate(&init_user_ns, path->dentry, 0,
+		error = do_truncate(mnt_userns, path->dentry, 0,
 				    ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
 				    filp);
 	}
@@ -3118,6 +3120,7 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
 				  const struct open_flags *op,
 				  bool got_write)
 {
+	struct user_namespace *mnt_userns;
 	struct dentry *dir = nd->path.dentry;
 	struct inode *dir_inode = dir->d_inode;
 	int open_flag = op->open_flag;
@@ -3165,13 +3168,14 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
 	 */
 	if (unlikely(!got_write))
 		open_flag &= ~O_TRUNC;
+	mnt_userns = mnt_user_ns(nd->path.mnt);
 	if (open_flag & O_CREAT) {
 		if (open_flag & O_EXCL)
 			open_flag &= ~O_TRUNC;
 		if (!IS_POSIXACL(dir->d_inode))
 			mode &= ~current_umask();
 		if (likely(got_write))
-			create_error = may_o_create(&init_user_ns, &nd->path,
+			create_error = may_o_create(mnt_userns, &nd->path,
 						    dentry, mode);
 		else
 			create_error = -EROFS;
@@ -3207,8 +3211,9 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
 			error = -EACCES;
 			goto out_dput;
 		}
-		error = dir_inode->i_op->create(dir_inode, dentry, mode,
-						open_flag & O_EXCL);
+
+		error = dir_inode->i_op->create(mnt_userns, dir_inode, dentry,
+						mode, open_flag & O_EXCL);
 		if (error)
 			goto out_dput;
 	}
@@ -3316,6 +3321,7 @@ finish_lookup:
 static int do_open(struct nameidata *nd,
 		   struct file *file, const struct open_flags *op)
 {
+	struct user_namespace *mnt_userns;
 	int open_flag = op->open_flag;
 	bool do_truncate;
 	int acc_mode;
@@ -3328,12 +3334,13 @@ static int do_open(struct nameidata *nd,
 	}
 	if (!(file->f_mode & FMODE_CREATED))
 		audit_inode(nd->name, nd->path.dentry, 0);
+	mnt_userns = mnt_user_ns(nd->path.mnt);
 	if (open_flag & O_CREAT) {
 		if ((open_flag & O_EXCL) && !(file->f_mode & FMODE_CREATED))
 			return -EEXIST;
 		if (d_is_dir(nd->path.dentry))
 			return -EISDIR;
-		error = may_create_in_sticky(&init_user_ns, nd,
+		error = may_create_in_sticky(mnt_userns, nd,
 					     d_backing_inode(nd->path.dentry));
 		if (unlikely(error))
 			return error;
@@ -3353,13 +3360,13 @@ static int do_open(struct nameidata *nd,
 			return error;
 		do_truncate = true;
 	}
-	error = may_open(&init_user_ns, &nd->path, acc_mode, open_flag);
+	error = may_open(mnt_userns, &nd->path, acc_mode, open_flag);
 	if (!error && !(file->f_mode & FMODE_OPENED))
 		error = vfs_open(&nd->path, file);
 	if (!error)
 		error = ima_file_check(file, op->acc_mode);
 	if (!error && do_truncate)
-		error = handle_truncate(file);
+		error = handle_truncate(mnt_userns, file);
 	if (unlikely(error > 0)) {
 		WARN_ON(1);
 		error = -EINVAL;
@@ -3403,7 +3410,7 @@ struct dentry *vfs_tmpfile(struct user_namespace *mnt_userns,
 	child = d_alloc(dentry, &slash_name);
 	if (unlikely(!child))
 		goto out_err;
-	error = dir->i_op->tmpfile(dir, child, mode);
+	error = dir->i_op->tmpfile(mnt_userns, dir, child, mode);
 	if (error)
 		goto out_err;
 	error = -ENOENT;
@@ -3446,7 +3453,7 @@ static int do_tmpfile(struct nameidata *nd, unsigned flags,
 	path.dentry = child;
 	audit_inode(nd->name, child, 0);
 	/* Don't check for other permissions, the inode was just created */
-	error = may_open(&init_user_ns, &path, 0, op->open_flag);
+	error = may_open(mnt_userns, &path, 0, op->open_flag);
 	if (error)
 		goto out2;
 	file->f_path.mnt = path.mnt;
@@ -3690,7 +3697,7 @@ int vfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
 	if (error)
 		return error;
 
-	error = dir->i_op->mknod(dir, dentry, mode, dev);
+	error = dir->i_op->mknod(mnt_userns, dir, dentry, mode, dev);
 	if (!error)
 		fsnotify_create(dir, dentry);
 	return error;
@@ -3809,7 +3816,7 @@ int vfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
 	if (max_links && dir->i_nlink >= max_links)
 		return -EMLINK;
 
-	error = dir->i_op->mkdir(dir, dentry, mode);
+	error = dir->i_op->mkdir(mnt_userns, dir, dentry, mode);
 	if (!error)
 		fsnotify_mkdir(dir, dentry);
 	return error;
@@ -3834,7 +3841,8 @@ retry:
 	if (!error) {
 		struct user_namespace *mnt_userns;
 		mnt_userns = mnt_user_ns(path.mnt);
-		error = vfs_mkdir(mnt_userns, path.dentry->d_inode, dentry, mode);
+		error = vfs_mkdir(mnt_userns, path.dentry->d_inode, dentry,
+				  mode);
 	}
 	done_path_create(&path, dentry);
 	if (retry_estale(error, lookup_flags)) {
@@ -4087,7 +4095,8 @@ retry_deleg:
 		if (error)
 			goto exit2;
 		mnt_userns = mnt_user_ns(path.mnt);
-		error = vfs_unlink(mnt_userns, path.dentry->d_inode, dentry, &delegated_inode);
+		error = vfs_unlink(mnt_userns, path.dentry->d_inode, dentry,
+				   &delegated_inode);
 exit2:
 		dput(dentry);
 	}
@@ -4166,7 +4175,7 @@ int vfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 	if (error)
 		return error;
 
-	error = dir->i_op->symlink(dir, dentry, oldname);
+	error = dir->i_op->symlink(mnt_userns, dir, dentry, oldname);
 	if (!error)
 		fsnotify_create(dir, dentry);
 	return error;
@@ -4357,13 +4366,13 @@ retry:
 	error = -EXDEV;
 	if (old_path.mnt != new_path.mnt)
 		goto out_dput;
-	error = may_linkat(&init_user_ns, &old_path);
+	mnt_userns = mnt_user_ns(new_path.mnt);
+	error = may_linkat(mnt_userns, &old_path);
 	if (unlikely(error))
 		goto out_dput;
 	error = security_path_link(old_path.dentry, &new_path, new_dentry);
 	if (error)
 		goto out_dput;
-	mnt_userns = mnt_user_ns(new_path.mnt);
 	error = vfs_link(old_path.dentry, mnt_userns, new_path.dentry->d_inode,
 			 new_dentry, &delegated_inode);
 out_dput:
@@ -4542,8 +4551,8 @@ int vfs_rename(struct renamedata *rd)
 		if (error)
 			goto out;
 	}
-	error = old_dir->i_op->rename(old_dir, old_dentry,
-				       new_dir, new_dentry, flags);
+	error = old_dir->i_op->rename(rd->new_mnt_userns, old_dir, old_dentry,
+				      new_dir, new_dentry, flags);
 	if (error)
 		goto out;