File 0001-Fix-race-condition-in-discovering-outputs.patch of Package xscreensaver.24903

From 86c84c08e6dc025c0a75248ffe02919406bd2e20 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
 <marmarek@invisiblethingslab.com>
Date: Tue, 29 Jun 2021 01:48:23 +0200
Subject: [PATCH] Fix race condition in discovering outputs
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Organization: Invisible Things Lab
Cc: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

The randr_scan_monitors() function first counts available outputs, then
allocates monitors array and fills it. The issue is that new outputs
could be connected between allocating the array and filling it - and the
function retrieves outputs count the second time while filling the
array. This means the monitors array can be overflown.

Fix this by retrieving outputs up to the count initially discovered,
even if later check returns more outputs. This will possibly loose some
outputs, but those extra outputs appearing there should generate another
RANDR event, and randr_scan_monitors() should be called again - at which
point it will handle them correctly.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
 driver/screens.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/driver/screens.c b/driver/screens.c
index ed43a8d9..8c0d8a41 100644
--- a/driver/screens.c
+++ b/driver/screens.c
@@ -447,7 +447,7 @@ randr_scan_monitors (Display *dpy, char **errP)
           int k;
           XRRScreenResources *res = 
             XRRGetScreenResources (dpy, RootWindowOfScreen (screen));
-          for (k = 0; k < res->noutput; k++, j++)
+          for (k = 0; k < res->noutput && j < nscreens; k++, j++)
             {
               monitor *m = (monitor *) calloc (1, sizeof (monitor));
               XRROutputInfo *rroi = XRRGetOutputInfo (dpy, res, 
-- 
2.31.1