Revert "ovl: relax permission checking on underlying layers"

Miklos Szeredi · Miklos Szeredi · commit ec7ba118b940 · 2018-12-04T11:31:30.000+01:00
This reverts commit 007ea44. The commit broke some selinux-testsuite cases, and it looks like there's no straightforward fix keeping the direction of this patch, so revert for now. The original patch was trying to fix the consistency of permission checks, and not an observed bug. So reverting should be safe. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
@@ -286,22 +286,13 @@ int ovl_permission(struct inode *inode, int mask)
 	if (err)
 		return err;
 
-	/* 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) {
+	old_cred = ovl_override_creds(inode->i_sb);
+	if (!upperinode &&
+	    !special_file(realinode->i_mode) && 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);
 
