Merge tag 'ovl-update-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs updates from Miklos Szeredi:
 "A mix of fixes and cleanups"

* tag 'ovl-update-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: automatically enable redirect_dir on metacopy=on
  ovl: check whiteout in ovl_create_over_whiteout()
  ovl: using posix_acl_xattr_size() to get size instead of posix_acl_to_xattr()
  ovl: abstract ovl_inode lock with a helper
  ovl: remove the 'locked' argument of ovl_nlink_{start,end}
  ovl: relax requirement for non null uuid of lower fs
  ovl: fold copy-up helpers into callers
  ovl: untangle copy up call chain
  ovl: relax permission checking on underlying layers
  ovl: fix recursive oi->lock in ovl_link()
  vfs: fix FIGETBSZ ioctl on an overlayfs file
  ovl: clean up error handling in ovl_get_tmpfile()
  ovl: fix error handling in ovl_verify_set_fh()

1 files changed, 13 insertions, 4 deletions

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 3b7ed5d2279c..6bcc9dedc342 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -286,13 +286,22 @@ int ovl_permission(struct inode *inode, int mask)
 	if (err)
 		return err;
 
-	old_cred = ovl_override_creds(inode->i_sb);
-	if (!upperinode &&
-	    !special_file(realinode->i_mode) && mask & MAY_WRITE) {
+	/* No need to do any access on underlying for special files */
+	if (special_file(realinode->i_mode))
+		return 0;
+
+	/* No need to access underlying for execute */
+	mask &= ~MAY_EXEC;
+	if ((mask & (MAY_READ | MAY_WRITE)) == 0)
+		return 0;
+
+	/* Lower files get copied up, so turn write access into read */
+	if (!upperinode && mask & MAY_WRITE) {
 		mask &= ~(MAY_WRITE | MAY_APPEND);
-		/* Make sure mounter can read file for copy up later */
 		mask |= MAY_READ;
 	}
+
+	old_cred = ovl_override_creds(inode->i_sb);
 	err = inode_permission(realinode, mask);
 	revert_creds(old_cred);