Subject: Re: bug#58334: 29.0.50; ASAN heap use after free in gui_produce_glyphs

From: Po Lu <[email-masked]>
Date: Fri, 07 Oct 2022 08:46:15 +0800

Gerd Möllmann <[email-masked]> writes:

>     #0 0x1033f2ca8 in wrap_malloc+0x94 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x3eca8)
>     #1 0x1005af4f4 in lmalloc alloc.c:1361
>     #2 0x1005af40c in xmalloc alloc.c:751
>     #3 0x1003f92b4 in make_realized_face xfaces.c:4471
>     #4 0x1003f5c00 in realize_gui_face xfaces.c:6023
>     #5 0x1003e4000 in realize_face xfaces.c:5954

[...]

>     #14 0x1005592d8 in Fvertical_motion indent.c:2241

I'm pretty sure the right fix is to block input around realize_face and
Fvertical_motion, since that code is clearly not reentrant.

> The problem here, it seems to me, is that the redisplay done in
> -[EmacsView layoutSublayersOfLayer:] nsterm.m:8675, frees realized faces
> at a moment that the code doesn't cannot expect.

Also, how come layoutSublayersOfLayer is called so often?  AFAIU it's
only there to coax the system into actually resizing Emacs while the
system blocks the input loop from returning control to Emacs, which
should only happen during drag-to-resize.