On Wed, Jun 03, 2020 at 06:23:26PM +0200, Adrian Reber wrote:
...

 
 /*
- * Only allow CAP_SYS_ADMIN to follow the links, due to concerns about how the
- * symlinks may be used to bypass permissions on ancestor directories in the
- * path to the file in question.
+ * Only allow CAP_SYS_ADMIN and CAP_CHECKPOINT_RESTORE to follow the links, due
+ * to concerns about how the symlinks may be used to bypass permissions on
+ * ancestor directories in the path to the file in question.
  */
 static const char *
 proc_map_files_get_link(struct dentry *dentry,
 			struct inode *inode,
 		        struct delayed_call *done)
 {
-	if (!capable(CAP_SYS_ADMIN))
+	if (!(capable(CAP_SYS_ADMIN) || capable(CAP_CHECKPOINT_RESTORE)))
 		return ERR_PTR(-EPERM);

You know, I'm still not sure if we need this capable() check at all since
we have proc_fd_access_allowed() called but anyway can we please make this
if() condition more explicit

	if (!capable(CAP_SYS_ADMIN) && !capable(CAP_CHECKPOINT_RESTORE))
		return ERR_PTR(-EPERM);

though I won't insist. And I'll reread the series a bit later once I've
some spare time to.