fs: port ->permission() to pass 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, 32 insertions, 28 deletions

diff --git a/fs/xattr.c b/fs/xattr.c
index e69a2935ef58..d056d9ac247a 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -82,7 +82,7 @@ xattr_resolve_name(struct inode *inode, const char **name)
 
 /**
  * may_write_xattr - check whether inode allows writing xattr
- * @mnt_userns:	User namespace of the mount the inode was found from
+ * @idmap: idmap of the mount the inode was found from
  * @inode: the inode on which to set an xattr
  *
  * Check whether the inode allows writing xattrs. Specifically, we can never
@@ -94,13 +94,13 @@ xattr_resolve_name(struct inode *inode, const char **name)
  *
  * Return: On success zero is returned. On error a negative errno is returned.
  */
-int may_write_xattr(struct user_namespace *mnt_userns, struct inode *inode)
+int may_write_xattr(struct mnt_idmap *idmap, struct inode *inode)
 {
 	if (IS_IMMUTABLE(inode))
 		return -EPERM;
 	if (IS_APPEND(inode))
 		return -EPERM;
-	if (HAS_UNMAPPED_ID(mnt_userns, inode))
+	if (HAS_UNMAPPED_ID(idmap, inode))
 		return -EPERM;
 	return 0;
 }
@@ -110,13 +110,15 @@ int may_write_xattr(struct user_namespace *mnt_userns, struct inode *inode)
  * because different namespaces have very different rules.
  */
 static int
-xattr_permission(struct user_namespace *mnt_userns, struct inode *inode,
+xattr_permission(struct mnt_idmap *idmap, struct inode *inode,
 		 const char *name, int mask)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
+
 	if (mask & MAY_WRITE) {
 		int ret;
 
-		ret = may_write_xattr(mnt_userns, inode);
+		ret = may_write_xattr(idmap, inode);
 		if (ret)
 			return ret;
 	}
@@ -152,7 +154,7 @@ xattr_permission(struct user_namespace *mnt_userns, struct inode *inode,
 			return -EPERM;
 	}
 
-	return inode_permission(mnt_userns, inode, mask);
+	return inode_permission(idmap, inode, mask);
 }
 
 /*
@@ -264,7 +266,7 @@ int __vfs_setxattr_noperm(struct user_namespace *mnt_userns,
  * __vfs_setxattr_locked - set an extended attribute while holding the inode
  * lock
  *
- *  @mnt_userns: user namespace of the mount of the target inode
+ *  @idmap: idmap of the mount of the target inode
  *  @dentry: object to perform setxattr on
  *  @name: xattr name to set
  *  @value: value to set @name to
@@ -274,14 +276,15 @@ int __vfs_setxattr_noperm(struct user_namespace *mnt_userns,
  *  a delegation was broken on, NULL if none.
  */
 int
-__vfs_setxattr_locked(struct user_namespace *mnt_userns, struct dentry *dentry,
+__vfs_setxattr_locked(struct mnt_idmap *idmap, struct dentry *dentry,
 		      const char *name, const void *value, size_t size,
 		      int flags, struct inode **delegated_inode)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	struct inode *inode = dentry->d_inode;
 	int error;
 
-	error = xattr_permission(mnt_userns, inode, name, MAY_WRITE);
+	error = xattr_permission(idmap, inode, name, MAY_WRITE);
 	if (error)
 		return error;
 
@@ -303,9 +306,10 @@ out:
 EXPORT_SYMBOL_GPL(__vfs_setxattr_locked);
 
 int
-vfs_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+vfs_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
 	     const char *name, const void *value, size_t size, int flags)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	struct inode *inode = dentry->d_inode;
 	struct inode *delegated_inode = NULL;
 	const void  *orig_value = value;
@@ -320,7 +324,7 @@ vfs_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 
 retry_deleg:
 	inode_lock(inode);
-	error = __vfs_setxattr_locked(mnt_userns, dentry, name, value, size,
+	error = __vfs_setxattr_locked(idmap, dentry, name, value, size,
 				      flags, &delegated_inode);
 	inode_unlock(inode);
 
@@ -337,19 +341,19 @@ retry_deleg:
 EXPORT_SYMBOL_GPL(vfs_setxattr);
 
 static ssize_t
-xattr_getsecurity(struct user_namespace *mnt_userns, struct inode *inode,
+xattr_getsecurity(struct mnt_idmap *idmap, struct inode *inode,
 		  const char *name, void *value, size_t size)
 {
 	void *buffer = NULL;
 	ssize_t len;
 
 	if (!value || !size) {
-		len = security_inode_getsecurity(mnt_userns, inode, name,
+		len = security_inode_getsecurity(idmap, inode, name,
 						 &buffer, false);
 		goto out_noalloc;
 	}
 
-	len = security_inode_getsecurity(mnt_userns, inode, name, &buffer,
+	len = security_inode_getsecurity(idmap, inode, name, &buffer,
 					 true);
 	if (len < 0)
 		return len;
@@ -374,7 +378,7 @@ out_noalloc:
  * Returns the result of alloc, if failed, or the getxattr operation.
  */
 int
-vfs_getxattr_alloc(struct user_namespace *mnt_userns, struct dentry *dentry,
+vfs_getxattr_alloc(struct mnt_idmap *idmap, struct dentry *dentry,
 		   const char *name, char **xattr_value, size_t xattr_size,
 		   gfp_t flags)
 {
@@ -383,7 +387,7 @@ vfs_getxattr_alloc(struct user_namespace *mnt_userns, struct dentry *dentry,
 	char *value = *xattr_value;
 	int error;
 
-	error = xattr_permission(mnt_userns, inode, name, MAY_READ);
+	error = xattr_permission(idmap, inode, name, MAY_READ);
 	if (error)
 		return error;
 
@@ -427,13 +431,13 @@ __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
 EXPORT_SYMBOL(__vfs_getxattr);
 
 ssize_t
-vfs_getxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+vfs_getxattr(struct mnt_idmap *idmap, struct dentry *dentry,
 	     const char *name, void *value, size_t size)
 {
 	struct inode *inode = dentry->d_inode;
 	int error;
 
-	error = xattr_permission(mnt_userns, inode, name, MAY_READ);
+	error = xattr_permission(idmap, inode, name, MAY_READ);
 	if (error)
 		return error;
 
@@ -444,7 +448,7 @@ vfs_getxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 	if (!strncmp(name, XATTR_SECURITY_PREFIX,
 				XATTR_SECURITY_PREFIX_LEN)) {
 		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
-		int ret = xattr_getsecurity(mnt_userns, inode, suffix, value,
+		int ret = xattr_getsecurity(idmap, inode, suffix, value,
 					    size);
 		/*
 		 * Only overwrite the return value if a security module
@@ -503,21 +507,22 @@ EXPORT_SYMBOL(__vfs_removexattr);
  * __vfs_removexattr_locked - set an extended attribute while holding the inode
  * lock
  *
- *  @mnt_userns: user namespace of the mount of the target inode
+ *  @idmap: idmap of the mount of the target inode
  *  @dentry: object to perform setxattr on
  *  @name: name of xattr to remove
  *  @delegated_inode: on return, will contain an inode pointer that
  *  a delegation was broken on, NULL if none.
  */
 int
-__vfs_removexattr_locked(struct user_namespace *mnt_userns,
+__vfs_removexattr_locked(struct mnt_idmap *idmap,
 			 struct dentry *dentry, const char *name,
 			 struct inode **delegated_inode)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	struct inode *inode = dentry->d_inode;
 	int error;
 
-	error = xattr_permission(mnt_userns, inode, name, MAY_WRITE);
+	error = xattr_permission(idmap, inode, name, MAY_WRITE);
 	if (error)
 		return error;
 
@@ -542,7 +547,7 @@ out:
 EXPORT_SYMBOL_GPL(__vfs_removexattr_locked);
 
 int
-vfs_removexattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+vfs_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
 		const char *name)
 {
 	struct inode *inode = dentry->d_inode;
@@ -551,7 +556,7 @@ vfs_removexattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 
 retry_deleg:
 	inode_lock(inode);
-	error = __vfs_removexattr_locked(mnt_userns, dentry,
+	error = __vfs_removexattr_locked(idmap, dentry,
 					 name, &delegated_inode);
 	inode_unlock(inode);
 
@@ -605,7 +610,7 @@ int do_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
 		return do_set_acl(idmap, dentry, ctx->kname->name,
 				  ctx->kvalue, ctx->size);
 
-	return vfs_setxattr(mnt_idmap_owner(idmap), dentry, ctx->kname->name,
+	return vfs_setxattr(idmap, dentry, ctx->kname->name,
 			ctx->kvalue, ctx->size, ctx->flags);
 }
 
@@ -714,8 +719,7 @@ do_getxattr(struct mnt_idmap *idmap, struct dentry *d,
 	if (is_posix_acl_xattr(ctx->kname->name))
 		error = do_get_acl(idmap, d, kname, ctx->kvalue, ctx->size);
 	else
-		error = vfs_getxattr(mnt_idmap_owner(idmap), d, kname,
-				     ctx->kvalue, ctx->size);
+		error = vfs_getxattr(idmap, d, kname, ctx->kvalue, ctx->size);
 	if (error > 0) {
 		if (ctx->size && copy_to_user(ctx->value, ctx->kvalue, error))
 			error = -EFAULT;
@@ -894,7 +898,7 @@ removexattr(struct mnt_idmap *idmap, struct dentry *d,
 	if (is_posix_acl_xattr(kname))
 		return vfs_remove_acl(idmap, d, kname);
 
-	return vfs_removexattr(mnt_idmap_owner(idmap), d, kname);
+	return vfs_removexattr(idmap, d, kname);
 }
 
 static int path_removexattr(const char __user *pathname,