Merge tag 'fs.fuse.acl.v6.2-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping

Pull fuse ACL fix from Christian Brauner:
 "The new posix acl API doesn't depend on the xattr handler
  infrastructure anymore and instead only relies on the posix acl inode
  operations. As a result daemons without FUSE_POSIX_ACL are unable to
  use posix acls like they used to.

  Fix this by copying what we did for overlayfs during the posix acl api
  conversion. Make fuse implement a dedicated ->get_inode_acl() method
  as does overlayfs. Fuse can then also uses this to express different
  needs for vfs permission checking during lookup and acl based
  retrieval via the regular system call path.

  This allows fuse to continue to refuse retrieving posix acls for
  daemons that don't set FUSE_POSXI_ACL for permission checking while
  also allowing a fuse server to retrieve it via the usual system calls"

* tag 'fs.fuse.acl.v6.2-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping:
  fuse: fixes after adapting to new posix acl api

1 files changed, 61 insertions, 7 deletions

diff --git a/fs/fuse/acl.c b/fs/fuse/acl.c
index a4850aee2639..ad670369955f 100644
--- a/fs/fuse/acl.c
+++ b/fs/fuse/acl.c
@@ -11,9 +11,10 @@
 #include <linux/posix_acl.h>
 #include <linux/posix_acl_xattr.h>
 
-struct posix_acl *fuse_get_acl(struct inode *inode, int type, bool rcu)
+static struct posix_acl *__fuse_get_acl(struct fuse_conn *fc,
+					struct user_namespace *mnt_userns,
+					struct inode *inode, int type, bool rcu)
 {
-	struct fuse_conn *fc = get_fuse_conn(inode);
 	int size;
 	const char *name;
 	void *value = NULL;
@@ -25,7 +26,7 @@ struct posix_acl *fuse_get_acl(struct inode *inode, int type, bool rcu)
 	if (fuse_is_bad(inode))
 		return ERR_PTR(-EIO);
 
-	if (!fc->posix_acl || fc->no_getxattr)
+	if (fc->no_getxattr)
 		return NULL;
 
 	if (type == ACL_TYPE_ACCESS)
@@ -53,6 +54,46 @@ struct posix_acl *fuse_get_acl(struct inode *inode, int type, bool rcu)
 	return acl;
 }
 
+static inline bool fuse_no_acl(const struct fuse_conn *fc,
+			       const struct inode *inode)
+{
+	/*
+	 * Refuse interacting with POSIX ACLs for daemons that
+	 * don't support FUSE_POSIX_ACL and are not mounted on
+	 * the host to retain backwards compatibility.
+	 */
+	return !fc->posix_acl && (i_user_ns(inode) != &init_user_ns);
+}
+
+struct posix_acl *fuse_get_acl(struct user_namespace *mnt_userns,
+			       struct dentry *dentry, int type)
+{
+	struct inode *inode = d_inode(dentry);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	if (fuse_no_acl(fc, inode))
+		return ERR_PTR(-EOPNOTSUPP);
+
+	return __fuse_get_acl(fc, mnt_userns, inode, type, false);
+}
+
+struct posix_acl *fuse_get_inode_acl(struct inode *inode, int type, bool rcu)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	/*
+	 * FUSE daemons before FUSE_POSIX_ACL was introduced could get and set
+	 * POSIX ACLs without them being used for permission checking by the
+	 * vfs. Retain that behavior for backwards compatibility as there are
+	 * filesystems that do all permission checking for acls in the daemon
+	 * and not in the kernel.
+	 */
+	if (!fc->posix_acl)
+		return NULL;
+
+	return __fuse_get_acl(fc, &init_user_ns, inode, type, rcu);
+}
+
 int fuse_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
 		 struct posix_acl *acl, int type)
 {
@@ -64,7 +105,7 @@ int fuse_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
 	if (fuse_is_bad(inode))
 		return -EIO;
 
-	if (!fc->posix_acl || fc->no_setxattr)
+	if (fc->no_setxattr || fuse_no_acl(fc, inode))
 		return -EOPNOTSUPP;
 
 	if (type == ACL_TYPE_ACCESS)
@@ -99,7 +140,13 @@ int fuse_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
 			return ret;
 		}
 
-		if (!vfsgid_in_group_p(i_gid_into_vfsgid(&init_user_ns, inode)) &&
+		/*
+		 * Fuse daemons without FUSE_POSIX_ACL never changed the passed
+		 * through POSIX ACLs. Such daemons don't expect setgid bits to
+		 * be stripped.
+		 */
+		if (fc->posix_acl &&
+		    !vfsgid_in_group_p(i_gid_into_vfsgid(&init_user_ns, inode)) &&
 		    !capable_wrt_inode_uidgid(&init_user_ns, inode, CAP_FSETID))
 			extra_flags |= FUSE_SETXATTR_ACL_KILL_SGID;
 
@@ -108,8 +155,15 @@ int fuse_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
 	} else {
 		ret = fuse_removexattr(inode, name);
 	}
-	forget_all_cached_acls(inode);
-	fuse_invalidate_attr(inode);
+
+	if (fc->posix_acl) {
+		/*
+		 * Fuse daemons without FUSE_POSIX_ACL never cached POSIX ACLs
+		 * and didn't invalidate attributes. Retain that behavior.
+		 */
+		forget_all_cached_acls(inode);
+		fuse_invalidate_attr(inode);
+	}
 
 	return ret;
 }