Subject: Re: bug#58042: 29.0.50; ASAN use-after-free in re_match_2_internal

From: Po Lu <[email-masked]>
Date: Wed, 05 Oct 2022 20:48:25 +0800

Gerd Möllmann <[email-masked]> writes:

> I don't get an abort, but the ASAN error again

Interesting.

> ==67682==ERROR: AddressSanitizer: heap-use-after-free on address 0x000107130d00 at pc 0x0001002a481c bp 0x00016fdcc3c0 sp 0x00016fdcc3b8
> READ of size 8 at 0x000107130d00 thread T0
>     #0 0x1002a4818 in PSEUDOVECTORP lisp.h:1110
>     #1 0x1002a4888 in SYMBOL_WITH_POS_P lisp.h:1122
>     #2 0x10025a338 in EQ lisp.h:1342
>     #3 0x100280eb0 in run_window_change_functions window.c:3964
>     #4 0x1000f18c4 in redisplay_internal xdisp.c:16600
>     #5 0x100107bf8 in redisplay xdisp.c:16111
>     #6 0x10089364c in -[EmacsView layoutSublayersOfLayer:] nsterm.m:8661
>     #7 0x1900a9624 in CA::Layer::layout_if_needed(CA::Transaction*)+0x224 (QuartzCore:arm64e+0x20624)
>     #8 0x1901f661c in CA::Context::commit_transaction(CA::Transaction*,
>     double, double*)+0x1c0 (QuartzCore:arm6
>
> frame #8: 0x0000000100280eb4 emacs`run_window_change_functions at window.c:3964:7
>    3961		     (de-)selected as its frame's or the globally selected
>    3962		     window.  */
>    3963		  if (((frame_selected_change
> -> 3964			&& (EQ (window, old_selected_window)
>    3965			    || EQ (window, selected_window)))
>    3966		       || (frame_selected_window_change
>    3967			   && (EQ (window, FRAME_OLD_SELECTED_WINDOW (f))
>
> (lldb) p window
> (Lisp_Object) $18 = 0x00000001071c2935 (struct window *) $23 = 0x00000001071c2930
> (lldb) p old_selected_window
> (Lisp_Object) $24 = 0x0000000107130d05 (struct Lisp_Vector *) $28 = 0x0000000107130d00
>
> old_selected_window looks strange.  It's a global that is not
> staticpro'd

Isn't old_selected_window supposed to be kept in sync with
FRAME_OLD_SELECTED_WINDOW in old_selected_frame, with the latter being
removed once it is deleted?

Would someone who knows the window code well please take a look at this?