Possible regression in shm handling

Hi,

after upgrading my system from
FreeBSD 14.3-PRERELEASE stable/14-n271240-62c010b6514b GENERIC
to
FreeBSD 14.3-STABLE stable/14-n271620-b53120be1656 GENERIC

I noticed that firefox now reliably crashes (closing the firefox window, 
and the process appears to abort with SIGSEGV)
when trying to open a file upload dialog when using sway
(forcing firefox to use X11 by setting `WAYLAND_DISPLAY=`makes the whole 
session hang).

Ports packages involved:
drm-61-kmod-6.1.128.1403501_4
firefox-139.0.1_1,2 (but also happens with firefox-esr)
glib-2.84.1_2,2
gtk3-3.24.49
sway-1.11.r4

Firefox log output is always something like:
```
[Parent 1609, Main Thread] WARNING: Native Windows wider than 65535 
pixels are not supported: 'glib warning', file 
/wrkdirs/usr/ports/www/firefox/work/firefox-139.0.1/toolkit/xre/nsSigHandlers.cpp:201

(firefox:1609): Gdk-WARNING **: 17:37:32.563: Native Windows wider than 
65535 pixels are not supported
[Parent 1609, Main Thread] WARNING: Native Windows taller than 65535 
pixels are not supported: 'glib warning', file 
/wrkdirs/usr/ports/www/firefox/work/firefox-139.0.1/toolkit/xre/nsSigHandlers.cpp:201

(firefox:1609): Gdk-WARNING **: 17:37:32.563: Native Windows taller than 
65535 pixels are not supported
[Parent 1609, Main Thread] WARNING: 
../gdk/wayland/gdkdisplay-wayland.c:1372: Truncating shared memory file 
failed: Invalid argument: 'glib warning', file 
/wrkdirs/usr/ports/www/firefox/work/firefox-139.0.1/toolkit/xre/nsSigHandlers.cpp:201

(firefox:1609): Gdk-CRITICAL **: 17:37:32.702: 
../gdk/wayland/gdkdisplay-wayland.c:1372: Truncating shared memory file 
failed: Invalid argument
console.warn: LoginRecipes: "Falling back to a synchronous message for: 
file://."
Exiting due to channel error.
Exiting due to channel error.
Exiting due to channel error.
Exiting due to channel error.
Exiting due to channel error.
Exiting due to channel error.
Exiting due to channel error.
Exiting due to channel error.
Exiting due to channel error.
Exiting due to channel error.
Exiting due to channel error.
Exiting due to channel error.
zsh: segmentation fault (core dumped)  firefox
```

backtrace:
```
(gdb) bt
#0  0x0000000803eaf3a4 in wl_proxy_get_version () at 
/usr/local/lib/libwayland-client.so.0
#1  0x00000008034987f7 in ??? () at /usr/local/lib/libgdk-3.so.0
#2  0x00000008034a85af in ??? () at /usr/local/lib/libgdk-3.so.0
#3  0x00000008034a69c9 in ??? () at /usr/local/lib/libgdk-3.so.0
#4  0x000000080347c6a2 in ??? () at /usr/local/lib/libgdk-3.so.0
#5  0x000000080347cbce in gdk_window_begin_draw_frame () at 
/usr/local/lib/libgdk-3.so.0
#6  0x00000008032fd71b in ??? () at /usr/local/lib/libgtk-3.so.0
#7  0x0000000803198de3 in gtk_main_do_event () at 
/usr/local/lib/libgtk-3.so.0
#8  0x000000080346b8b1 in ??? () at /usr/local/lib/libgdk-3.so.0
#9  0x000000080347d7de in ??? () at /usr/local/lib/libgdk-3.so.0
#10 0x000000080347ddaa in ??? () at /usr/local/lib/libgdk-3.so.0
#11 0x000000080347e028 in ??? () at /usr/local/lib/libgdk-3.so.0
#12 0x0000000802b68f24 in ??? () at /usr/local/lib/libgobject-2.0.so.0
#13 0x0000000802b82082 in ??? () at /usr/local/lib/libgobject-2.0.so.0
#14 0x0000000802b82bbc in g_signal_emit () at 
/usr/local/lib/libgobject-2.0.so.0
#15 0x0000000803474fbf in ??? () at /usr/local/lib/libgdk-3.so.0
#16 0x000000080345f832 in ??? () at /usr/local/lib/libgdk-3.so.0
#17 0x00000008035d2a41 in ??? () at /usr/local/lib/libglib-2.0.so.0
#18 0x00000008035d7241 in ??? () at /usr/local/lib/libglib-2.0.so.0
#19 0x00000008035d76c7 in ??? () at /usr/local/lib/libglib-2.0.so.0
#20 0x00000008035d7766 in g_main_context_iteration () at 
/usr/local/lib/libglib-2.0.so.0
#21 0x000000080a236f68 in nsAppShell::ProcessNextNativeEvent(bool) () at 
/usr/local/lib/firefox/libxul.so
#22 0x000000080a187b86 in 
nsBaseAppShell::OnProcessNextEvent(nsIThreadInternal*, bool) () at 
/usr/local/lib/firefox/libxul.so
#23 0x000000080a187c6d in non-virtual thunk to 
nsBaseAppShell::OnProcessNextEvent(nsIThreadInternal*, bool) () at 
/usr/local/lib/firefox/libxul.so
#24 0x0000000806e94d28 in nsThread::ProcessNextEvent(bool, bool*) () at 
/usr/local/lib/firefox/libxul.so
#25 0x0000000806e98daf in NS_ProcessNextEvent(nsIThread*, bool) () at 
/usr/local/lib/firefox/libxul.so
#26 0x0000000807453d29 in 
mozilla::ipc::MessagePump::Run(base::MessagePump::Delegate*) () at 
/usr/local/lib/firefox/libxul.so
#27 0x000000080740b057 in MessageLoop::Run() () at 
/usr/local/lib/firefox/libxul.so
#28 0x000000080a1878a9 in nsBaseAppShell::Run() () at 
/usr/local/lib/firefox/libxul.so
#29 0x000000080a236ea1 in nsAppShell::Run() () at 
/usr/local/lib/firefox/libxul.so
#30 0x000000080aba4a69 in nsAppStartup::Run() () at 
/usr/local/lib/firefox/libxul.so
#31 0x000000080ac808a6 in XREMain::XRE_mainRun() () at 
/usr/local/lib/firefox/libxul.so
#32 0x000000080ac81039 in XREMain::XRE_main(int, char**, 
mozilla::BootstrapConfig const&) () at /usr/local/lib/firefox/libxul.so
#33 0x000000080ac815ea in XRE_main(int, char**, mozilla::BootstrapConfig 
const&) () at /usr/local/lib/firefox/libxul.so
#34 0x0000000001046fbc in main ()
```
(sorry, I have no clue how to get a properly installed gtk+-3 with debug 
symbols, rebuilding the port with `DEBUG` option didn't help.)

I also don't really know what exactly caused this, because besides 
happening shortly after an upgrade,
it didn't start immediately; earlier today it still worked, and then it 
just started failing at some point,
with no clue as to why (no amount of rebooting or using different 
packages/ports appeared to influence this).

Regards,
Ellen Zscheile