xquartz: Allocate each fbconfig separately

A change during the 1.20 development cycle resulted in fbconfigs being walked
and deallocated individually during __glXScreenDestroy.  This change
now avoids a use-after-free caused by that change.

==50859==ERROR: AddressSanitizer: heap-use-after-free on address 0x00010d3819c8 at pc 0x0001009d4230 bp 0x00016feca7a0 sp 0x00016feca798
READ of size 8 at 0x00010d3819c8 thread T5
    #0 0x1009d422c in __glXScreenDestroy glxscreens.c:448
    #1 0x10091cc98 in __glXAquaScreenDestroy indirect.c:510
    #2 0x1009d2734 in glxCloseScreen glxscreens.c:169
    #3 0x100740a24 in dix_main main.c:325
    #4 0x10023ed50 in server_thread quartzStartup.c:65
    #5 0x199ae7fd0 in _pthread_start+0x13c (libsystem_pthread.dylib:arm64e+0x6fd0)
    #6 0x199ae2d38 in thread_start+0x4 (libsystem_pthread.dylib:arm64e+0x1d38)

0x00010d3819c8 is located 200 bytes inside of 12800-byte region [0x00010d381900,0x00010d384b00)
freed by thread T5 here:
    #0 0x101477ba8 in wrap_free+0x98 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x3fba8)
    #1 0x1009d4240 in __glXScreenDestroy glxscreens.c:449
    #2 0x10091cc98 in __glXAquaScreenDestroy indirect.c:510
    #3 0x1009d2734 in glxCloseScreen glxscreens.c:169
    #4 0x100740a24 in dix_main main.c:325
    #5 0x10023ed50 in server_thread quartzStartup.c:65
    #6 0x199ae7fd0 in _pthread_start+0x13c (libsystem_pthread.dylib:arm64e+0x6fd0)
    #7 0x199ae2d38 in thread_start+0x4 (libsystem_pthread.dylib:arm64e+0x1d38)

previously allocated by thread T5 here:
    #0 0x101477e38 in wrap_calloc+0x9c (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x3fe38)
    #1 0x100925a40 in __glXAquaCreateVisualConfigs visualConfigs.c:116
    #2 0x10091cb24 in __glXAquaScreenProbe+0x224 (X11.bin:arm64+0x100730b24)
    #3 0x1009cd840 in xorgGlxServerInit glxext.c:528
    #4 0x10074539c in _CallCallbacks dixutils.c:743
    #5 0x100932a70 in CallCallbacks callback.h:83
    #6 0x100932478 in GlxExtensionInit vndext.c:244
    #7 0x10020a364 in InitExtensions miinitext.c:267
    #8 0x10073fe7c in dix_main main.c:197
    #9 0x10023ed50 in server_thread quartzStartup.c:65
    #10 0x199ae7fd0 in _pthread_start+0x13c (libsystem_pthread.dylib:arm64e+0x6fd0)
    #11 0x199ae2d38 in thread_start+0x4 (libsystem_pthread.dylib:arm64e+0x1d38)

Regressed-in: 4b0a3cbab131eb453e2b3fc0337121969258a7be
CC: Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
Signed-off-by: Jeremy Huddleston Sequoia <jeremyhu@apple.com>

1 files changed, 12 insertions, 14 deletions

diff --git a/hw/xquartz/GL/visualConfigs.c b/hw/xquartz/GL/visualConfigs.c
index 69b18f6a0..d810e2dfe 100644
--- a/hw/xquartz/GL/visualConfigs.c
+++ b/hw/xquartz/GL/visualConfigs.c
@@ -59,7 +59,7 @@
 /* Based originally on code from indirect.c which was based on code from i830_dri.c. */
 __GLXconfig *__glXAquaCreateVisualConfigs(int *numConfigsPtr, int screenNumber) {
     int numConfigs = 0;
-    __GLXconfig *visualConfigs, *c;
+    __GLXconfig *visualConfigs, *c, *l;
     struct glCapabilities caps;
     struct glCapabilitiesConfig *conf;
     int stereo, depth, aux, buffers, stencil, accum, color, msample;
@@ -113,14 +113,13 @@ __GLXconfig *__glXAquaCreateVisualConfigs(int *numConfigsPtr, int screenNumber)
     if(numConfigsPtr)
         *numConfigsPtr = numConfigs;
 
-    visualConfigs = calloc(sizeof(*visualConfigs), numConfigs);
-
-    if(NULL == visualConfigs) {
-        ErrorF("xcalloc failure when allocating visualConfigs\n");
-        freeGlCapabilities(&caps);
-        return NULL;
-    }
+    /* Note that as of 1.20.0, we cannot allocate all the configs at once.
+     * __glXScreenDestroy now walks all the fbconfigs and frees them one at a time.
+     * See 4b0a3cbab131eb453e2b3fc0337121969258a7be.
+     */
+    visualConfigs = calloc(sizeof(*visualConfigs), 1);
 
+    l = NULL;
     c = visualConfigs; /* current buffer */
     for(conf = caps.configurations; conf; conf = conf->next) {
         for(stereo = 0; stereo < (conf->stereo ? 2 : 1); ++stereo) {
@@ -137,7 +136,8 @@ __GLXconfig *__glXAquaCreateVisualConfigs(int *numConfigsPtr, int screenNumber)
                                         // Global
                                         c->visualID = -1;
                                         c->visualType = GLX_TRUE_COLOR;
-                                        c->next = c + 1;
+                                        c->next = calloc(sizeof(*visualConfigs), 1);
+                                        assert(c->next);
 
                                         c->level = 0;
                                         c->indexBits = 0;
@@ -260,6 +260,7 @@ __GLXconfig *__glXAquaCreateVisualConfigs(int *numConfigsPtr, int screenNumber)
                                         /* EXT_framebuffer_sRGB */
                                         c->sRGBCapable = GL_FALSE;
 
+                                        l = c;
                                         c = c->next;
                                     }
                                 }
@@ -271,11 +272,8 @@ __GLXconfig *__glXAquaCreateVisualConfigs(int *numConfigsPtr, int screenNumber)
         }
     }
 
-    (c-1)->next = NULL;
-
-    if (c - visualConfigs != numConfigs) {
-        FatalError("numConfigs calculation error in setVisualConfigs!  numConfigs is %d  i is %d\n", numConfigs, (int)(c - visualConfigs));
-    }
+    free(c);
+    l->next = NULL;
 
     freeGlCapabilities(&caps);
     return visualConfigs;