GLX invalid read/write on GLX contexts with tags

Running Xwayland in valgrind shows invalid reads/writes relative to GLX contexts.
Excerpt of valgrind logs

Syscall param writev(vector[...]) points to uninitialised byte(s)
   at 0x51131BD: writev (in /usr/lib64/libc-2.33.so)
   by 0x27AAAD: _XSERVTransSocketWritev (Xtranssock.c:2228)
   by 0x26F631: UnknownInlinedFun (Xtrans.c:914)
   by 0x26F631: FlushClient (io.c:887)
   by 0x2A37B0: UnknownInlinedFun (vndcmds.c:110)
   by 0x2A37B0: dispatch_GLXQueryVersion (vndcmds.c:101)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0x1fff0000c1 is on thread 1's stack
 in frame #3, created by dispatch_GLXQueryVersion (vndcmds.c:102)
 Uninitialised value was created by a stack allocation
   at 0x2A3740: dispatch_GLXQueryVersion (vndcmds.c:102)

Invalid read of size 4
   at 0x28461E: xorgGlxMakeCurrent (glxcmds.c:599)
   by 0x2A39FE: UnknownInlinedFun (vndcmds.c:161)
   by 0x2A39FE: CommonMakeCurrent (vndcmds.c:255)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0xb898854 is 100 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid read of size 4
   at 0x28463A: xorgGlxMakeCurrent (glxcmds.c:636)
   by 0x2A39FE: UnknownInlinedFun (vndcmds.c:161)
   by 0x2A39FE: CommonMakeCurrent (vndcmds.c:255)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0xb89885c is 108 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid read of size 1
   at 0x284641: xorgGlxMakeCurrent (glxcmds.c:636)
   by 0x2A39FE: UnknownInlinedFun (vndcmds.c:161)
   by 0x2A39FE: CommonMakeCurrent (vndcmds.c:255)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0xb898851 is 97 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid read of size 8
   at 0x28464E: xorgGlxMakeCurrent (glxcmds.c:643)
   by 0x2A39FE: UnknownInlinedFun (vndcmds.c:161)
   by 0x2A39FE: CommonMakeCurrent (vndcmds.c:255)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0xb898800 is 16 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid read of size 1
   at 0x284664: xorgGlxMakeCurrent (glxcmds.c:647)
   by 0x2A39FE: UnknownInlinedFun (vndcmds.c:161)
   by 0x2A39FE: CommonMakeCurrent (vndcmds.c:255)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0xb898851 is 97 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid read of size 1
   at 0x28487D: xorgGlxMakeCurrent (glxcmds.c:671)
   by 0x2A39FE: UnknownInlinedFun (vndcmds.c:161)
   by 0x2A39FE: CommonMakeCurrent (vndcmds.c:255)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0xb898850 is 96 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid write of size 8
   at 0x2846A7: xorgGlxMakeCurrent (glxcmds.c:672)
   by 0x2A39FE: UnknownInlinedFun (vndcmds.c:161)
   by 0x2A39FE: CommonMakeCurrent (vndcmds.c:255)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0xb898840 is 80 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid read of size 4
   at 0x284710: xorgGlxMakeCurrent (glxcmds.c:674)
   by 0x2A39FE: UnknownInlinedFun (vndcmds.c:161)
   by 0x2A39FE: CommonMakeCurrent (vndcmds.c:255)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0xb898848 is 88 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid read of size 4
   at 0x28461E: xorgGlxMakeCurrent (glxcmds.c:599)
   by 0x2A25A9: UnknownInlinedFun (vndext.c:168)
   by 0x2A25A9: GLXClientCallback (vndext.c:188)
   by 0x1B1F6B: _CallCallbacks (dixutils.c:743)
   by 0x1ABF83: UnknownInlinedFun (callback.h:83)
   by 0x1ABF83: CloseDownClient (dispatch.c:3487)
   by 0x275D40: ospoll_wait (ospoll.c:657)
   by 0x1ACE6F: UnknownInlinedFun (WaitFor.c:208)
   by 0x1ACE6F: Dispatch (dispatch.c:438)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0x5e63d64 is 100 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid read of size 4
   at 0x28463A: xorgGlxMakeCurrent (glxcmds.c:636)
   by 0x2A25A9: UnknownInlinedFun (vndext.c:168)
   by 0x2A25A9: GLXClientCallback (vndext.c:188)
   by 0x1B1F6B: _CallCallbacks (dixutils.c:743)
   by 0x1ABF83: UnknownInlinedFun (callback.h:83)
   by 0x1ABF83: CloseDownClient (dispatch.c:3487)
   by 0x275D40: ospoll_wait (ospoll.c:657)
   by 0x1ACE6F: UnknownInlinedFun (WaitFor.c:208)
   by 0x1ACE6F: Dispatch (dispatch.c:438)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0x5e63d6c is 108 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid read of size 1
   at 0x284641: xorgGlxMakeCurrent (glxcmds.c:636)
   by 0x2A25A9: UnknownInlinedFun (vndext.c:168)
   by 0x2A25A9: GLXClientCallback (vndext.c:188)
   by 0x1B1F6B: _CallCallbacks (dixutils.c:743)
   by 0x1ABF83: UnknownInlinedFun (callback.h:83)
   by 0x1ABF83: CloseDownClient (dispatch.c:3487)
   by 0x275D40: ospoll_wait (ospoll.c:657)
   by 0x1ACE6F: UnknownInlinedFun (WaitFor.c:208)
   by 0x1ACE6F: Dispatch (dispatch.c:438)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0x5e63d61 is 97 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid read of size 8
   at 0x28464E: xorgGlxMakeCurrent (glxcmds.c:643)
   by 0x2A25A9: UnknownInlinedFun (vndext.c:168)
   by 0x2A25A9: GLXClientCallback (vndext.c:188)
   by 0x1B1F6B: _CallCallbacks (dixutils.c:743)
   by 0x1ABF83: UnknownInlinedFun (callback.h:83)
   by 0x1ABF83: CloseDownClient (dispatch.c:3487)
   by 0x275D40: ospoll_wait (ospoll.c:657)
   by 0x1ACE6F: UnknownInlinedFun (WaitFor.c:208)
   by 0x1ACE6F: Dispatch (dispatch.c:438)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0x5e63d10 is 16 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid read of size 1
   at 0x284664: xorgGlxMakeCurrent (glxcmds.c:647)
   by 0x2A25A9: UnknownInlinedFun (vndext.c:168)
   by 0x2A25A9: GLXClientCallback (vndext.c:188)
   by 0x1B1F6B: _CallCallbacks (dixutils.c:743)
   by 0x1ABF83: UnknownInlinedFun (callback.h:83)
   by 0x1ABF83: CloseDownClient (dispatch.c:3487)
   by 0x275D40: ospoll_wait (ospoll.c:657)
   by 0x1ACE6F: UnknownInlinedFun (WaitFor.c:208)
   by 0x1ACE6F: Dispatch (dispatch.c:438)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0x5e63d61 is 97 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid read of size 1
   at 0x28487D: xorgGlxMakeCurrent (glxcmds.c:671)
   by 0x2A25A9: UnknownInlinedFun (vndext.c:168)
   by 0x2A25A9: GLXClientCallback (vndext.c:188)
   by 0x1B1F6B: _CallCallbacks (dixutils.c:743)
   by 0x1ABF83: UnknownInlinedFun (callback.h:83)
   by 0x1ABF83: CloseDownClient (dispatch.c:3487)
   by 0x275D40: ospoll_wait (ospoll.c:657)
   by 0x1ACE6F: UnknownInlinedFun (WaitFor.c:208)
   by 0x1ACE6F: Dispatch (dispatch.c:438)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0x5e63d60 is 96 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid write of size 8
   at 0x2846A7: xorgGlxMakeCurrent (glxcmds.c:672)
   by 0x2A25A9: UnknownInlinedFun (vndext.c:168)
   by 0x2A25A9: GLXClientCallback (vndext.c:188)
   by 0x1B1F6B: _CallCallbacks (dixutils.c:743)
   by 0x1ABF83: UnknownInlinedFun (callback.h:83)
   by 0x1ABF83: CloseDownClient (dispatch.c:3487)
   by 0x275D40: ospoll_wait (ospoll.c:657)
   by 0x1ACE6F: UnknownInlinedFun (WaitFor.c:208)
   by 0x1ACE6F: Dispatch (dispatch.c:438)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0x5e63d50 is 80 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)

Invalid read of size 4
   at 0x284710: xorgGlxMakeCurrent (glxcmds.c:674)
   by 0x2A25A9: UnknownInlinedFun (vndext.c:168)
   by 0x2A25A9: GLXClientCallback (vndext.c:188)
   by 0x1B1F6B: _CallCallbacks (dixutils.c:743)
   by 0x1ABF83: UnknownInlinedFun (callback.h:83)
   by 0x1ABF83: CloseDownClient (dispatch.c:3487)
   by 0x275D40: ospoll_wait (ospoll.c:657)
   by 0x1ACE6F: UnknownInlinedFun (WaitFor.c:208)
   by 0x1ACE6F: Dispatch (dispatch.c:438)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Address 0x5e63d58 is 88 bytes inside a block of size 200 free'd
   at 0x48430E4: free (vg_replace_malloc.c:755)
   by 0x27EDA7: UnknownInlinedFun (glxext.c:190)
   by 0x27EDA7: ContextGone (glxext.c:82)
   by 0x1CF7C1: doFreeResource.lto_priv.0 (resource.c:885)
   by 0x283EF2: __glXDisp_DestroyContext (glxcmds.c:451)
   by 0x2A1214: dispatch_DestroyContext (vnd_dispatch_stubs.c:82)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
 Block was alloc'd at
   at 0x4845464: calloc (vg_replace_malloc.c:1117)
   by 0x28767B: UnknownInlinedFun (glxcmds.c:222)
   by 0x28767B: __glXDisp_CreateContextAttribsARB (createcontext.c:321)
   by 0x2A3343: dispatch_CreateContextAttribsARB (vnd_dispatch_stubs.c:386)
   by 0x2A289F: GlxDispatchRequest (vndcmds.c:483)
   by 0x1AD219: Dispatch (dispatch.c:497)
   by 0x13EE48: UnknownInlinedFun (main.c:271)
   by 0x13EE48: main (stubmain.c:34)
Looks like we're accessing a context in glxMakeCurrent() after it's been destroyed.
Based on the source lines reported above, the context is prevglxc which is set to prevglxc = glxServer.getContextTagPrivate(client, tag);
So maybe there's more to it than !680 (merged)
CC: @ajax
Edited Jun 18, 2021 by Olivier Fourdan
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GLX invalid read/write on GLX contexts with tags
