From 26dc1953d74a81edba1d5570d3e43fb6ea752fd0 Mon Sep 17 00:00:00 2001
From: "Perneel, Luc" <Luc.Perneel@barco.com>
Date: Tue, 28 Nov 2017 17:37:45 +0100
Subject: [PATCH] Modes handling: fix memory leak on xrandr usage.

In Xorg there is a memory leak each time xrandr is used.
This is easy to test by issuing following command:

$ while true ; do xrandr --verbose > /dev/null ; done

This will gradually let X take more memory until the oom killer pops in.
Reason is that each time the Monitor->Modes list grows, without pruning
duplicates. This patch fixes this.

An alternative solution could be to cleanup the list before retrieving
a new one (instead of attaching both).
---
 hw/xfree86/common/xf86Config.c   | 23 ++---------------------
 hw/xfree86/common/xf86str.h      |  1 -
 hw/xfree86/modes/xf86EdidModes.c | 20 +++++---------------
 3 files changed, 7 insertions(+), 37 deletions(-)

diff --git a/hw/xfree86/common/xf86Config.c b/hw/xfree86/common/xf86Config.c
index 21daf1a..a6181a1 100644
--- a/hw/xfree86/common/xf86Config.c
+++ b/hw/xfree86/common/xf86Config.c
@@ -1936,7 +1936,7 @@ static Bool
 configMonitor(MonPtr monitorp, XF86ConfMonitorPtr conf_monitor)
 {
     int count;
-    DisplayModePtr mode, last = NULL;
+    DisplayModePtr mode;
     XF86ConfModeLinePtr cmodep;
     XF86ConfModesPtr modes;
     XF86ConfModesLinkPtr modeslnk = conf_monitor->mon_modes_sect_lst;
@@ -1949,7 +1949,6 @@ configMonitor(MonPtr monitorp, XF86ConfMonitorPtr conf_monitor)
     monitorp->vendor = conf_monitor->mon_vendor;
     monitorp->model = conf_monitor->mon_modelname;
     monitorp->Modes = NULL;
-    monitorp->Last = NULL;
     monitorp->gamma = zeros;
     monitorp->widthmm = conf_monitor->mon_width;
     monitorp->heightmm = conf_monitor->mon_height;
@@ -2018,24 +2017,9 @@ configMonitor(MonPtr monitorp, XF86ConfMonitorPtr conf_monitor)
         mode->HSkew = cmodep->ml_hskew;
         mode->VScan = cmodep->ml_vscan;
         mode->name = xnfstrdup(cmodep->ml_identifier);
-        if (last) {
-            mode->prev = last;
-            last->next = mode;
-        }
-        else {
-            /*
-             * this is the first mode
-             */
-            monitorp->Modes = mode;
-            mode->prev = NULL;
-        }
-        last = mode;
+        monitorp->Modes = xf86ModesAdd( monitorp->Modes, mode);
         cmodep = (XF86ConfModeLinePtr) cmodep->list.next;
     }
-    if (last) {
-        last->next = NULL;
-    }
-    monitorp->Last = last;
 
     /* add the (VESA) default modes */
     if (!addDefaultModes(monitorp))
@@ -2315,20 +2299,17 @@ static Bool
 addDefaultModes(MonPtr monitorp)
 {
     DisplayModePtr mode;
-    DisplayModePtr last = monitorp->Last;
     int i = 0;
 
     for (i = 0; i < xf86NumDefaultModes; i++) {
         mode = xf86DuplicateMode(&xf86DefaultModes[i]);
         if (!modeIsPresent(mode, monitorp)) {
             monitorp->Modes = xf86ModesAdd(monitorp->Modes, mode);
-            last = mode;
         }
         else {
             free(mode);
         }
     }
-    monitorp->Last = last;
 
     return TRUE;
 }
diff --git a/hw/xfree86/common/xf86str.h b/hw/xfree86/common/xf86str.h
index bfcb75e..1c083c7 100644
--- a/hw/xfree86/common/xf86str.h
+++ b/hw/xfree86/common/xf86str.h
@@ -131,7 +131,6 @@ typedef struct {
     int nVrefresh;
     range vrefresh[MAX_VREFRESH];
     DisplayModePtr Modes;       /* Start of the monitor's mode list */
-    DisplayModePtr Last;        /* End of the monitor's mode list */
     Gamma gamma;                /* Gamma of the monitor */
     int widthmm;
     int heightmm;
diff --git a/hw/xfree86/modes/xf86EdidModes.c b/hw/xfree86/modes/xf86EdidModes.c
index f0e1e97..261ff8a 100644
--- a/hw/xfree86/modes/xf86EdidModes.c
+++ b/hw/xfree86/modes/xf86EdidModes.c
@@ -1198,21 +1198,11 @@ xf86EdidMonitorSet(int scrnIndex, MonPtr Monitor, xf86MonPtr DDC)
         if (!Monitor->nHsync || !Monitor->nVrefresh)
             DDCGuessRangesFromModes(scrnIndex, Monitor, Modes);
 
-        /* look for last Mode */
-        Mode = Modes;
-
-        while (Mode->next)
-            Mode = Mode->next;
-
         /* add to MonPtr */
-        if (Monitor->Modes) {
-            Monitor->Last->next = Modes;
-            Modes->prev = Monitor->Last;
-            Monitor->Last = Mode;
-        }
-        else {
-            Monitor->Modes = Modes;
-            Monitor->Last = Mode;
-        }
+        Monitor->Modes = xf86ModesAdd( Monitor->Modes, Modes);
+
+        /* prune doubles: otherwise this list will grow ad infinitum
+           until out of memory.... */
+        xf86PruneDuplicateModes(Monitor->Modes);
     }
 }
-- 
2.1.4