Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs fixes from Miklos Szeredi:
 "Fix two more POSIX ACL bugs introduced in 4.8 and add a missing fsync
  during copy up to prevent possible data loss"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: fsync after copy-up
  ovl: fix get_acl() on tmpfs
  ovl: update S_ISGID when setting posix ACLs

3 files changed, 17 insertions, 3 deletions

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index aeb60f791418..36795eed40b0 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -178,6 +178,8 @@ static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
                 len -= bytes;
         }
 
+        if (!error)
+                error = vfs_fsync(new_file, 0);
         fput(new_file);
 out_fput:
         fput(old_file);
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index c58f01babf30..7fb53d055537 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -270,9 +270,6 @@ struct posix_acl *ovl_get_acl(struct inode *inode, int type)
         if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
                 return NULL;
 
-        if (!realinode->i_op->get_acl)
-                return NULL;
-
         old_cred = ovl_override_creds(inode->i_sb);
         acl = get_acl(realinode, type);
         revert_creds(old_cred);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index bcf3965be819..edd46a0e951d 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1037,6 +1037,21 @@ ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
 
         posix_acl_release(acl);
 
+        /*
+         * Check if sgid bit needs to be cleared (actual setacl operation will
+         * be done with mounter's capabilities and so that won't do it for us).
+         */
+        if (unlikely(inode->i_mode & S_ISGID) &&
+            handler->flags == ACL_TYPE_ACCESS &&
+            !in_group_p(inode->i_gid) &&
+            !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
+                struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
+
+                err = ovl_setattr(dentry, &iattr);
+                if (err)
+                        return err;
+        }
+
         err = ovl_xattr_set(dentry, handler->name, value, size, flags);
         if (!err)
                 ovl_copyattr(ovl_inode_real(inode, NULL), inode);