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

From: Eli Zaretskii <[email-masked]>
Date: Wed, 05 Oct 2022 12:23:20 +0300

> From: Gerd Möllmann <[email-masked]>
> Cc: [email-masked]
> Date: Wed, 05 Oct 2022 11:00:00 +0200
> 
> ==45724==ERROR: AddressSanitizer: heap-use-after-free on address 0x000107130d00 at pc 0x0001002a4b04 bp 0x00016fd155e0 sp 0x00016fd155d8
> READ of size 8 at 0x000107130d00 thread T0
>     #0 0x1002a4b00 in PSEUDOVECTORP lisp.h:1110
>     #1 0x1002a4b70 in SYMBOL_WITH_POS_P lisp.h:1122
>     #2 0x10025a620 in EQ lisp.h:1342
>     #3 0x100281198 in run_window_change_functions window.c:3964
>     #4 0x1000f1bac in redisplay_internal xdisp.c:16600
>     #5 0x100107ee0 in redisplay xdisp.c:16111
>     #6 0x10089366c 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:arm64e+0x16d61c)
>     #9 0x19008b4c8 in CA::Transaction::commit()+0x2bc (QuartzCore:arm64e+0x24c8)
>     #10 0x18bee1698 in __62+[CATransaction(NSCATransaction) NS_setFlushesWithDisplayLink]_block_invoke+0x12c (AppKit:arm64e+0x1ac698)
>     #11 0x18c646754 in ___NSRunLoopObserverCreateWithHandler_block_invoke+0x3c (AppKit:arm64e+0x911754)
>     #12 0x1892101a0 in __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__+0x20 (CoreFoundation:arm64e+0x841a0)
>     #13 0x18920fff0 in __CFRunLoopDoObservers+0x24c (CoreFoundation:arm64e+0x83ff0)
>     #14 0x18920f524 in __CFRunLoopRun+0x300 (CoreFoundation:arm64e+0x83524)
>     #15 0x18920ea80 in CFRunLoopRunSpecific+0x254 (CoreFoundation:arm64e+0x82a80)
>     #16 0x191e4e334 in RunCurrentEventLoopInMode+0x120 (HIToolbox:arm64e+0x32334)
>     #17 0x191e4dfc0 in ReceiveNextEventCommon+0x140 (HIToolbox:arm64e+0x31fc0)
>     #18 0x191e4de64 in _BlockUntilNextEventMatchingListInModeWithFilter+0x44 (HIToolbox:arm64e+0x31e64)
>     #19 0x18bd76518 in _DPSNextEvent+0x358 (AppKit:arm64e+0x41518)
>     #20 0x18bd74e10 in -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:]+0x52c (AppKit:arm64e+0x3fe10)
>     #21 0x18bd66fdc in -[NSApplication run]+0x250 (AppKit:arm64e+0x31fdc)
>     #22 0x100870bd0 in -[EmacsApp run] nsterm.m:5799
>     #23 0x1008c7b2c in ns_read_socket_1 nsterm.m:4679
>     #24 0x1008ae550 in ns_read_socket nsterm.m:4697
>     #25 0x100437394 in gobble_input keyboard.c:7379
>     #26 0x100438bfc in handle_async_input keyboard.c:7610
>     #27 0x100438bdc in process_pending_signals keyboard.c:7624
>     #28 0x10064bd90 in probably_quit eval.c:1657
>     #29 0x10065fe6c in maybe_quit lisp.h:3737
>     #30 0x10066cb7c in Fmemq fns.c:1837
>     #31 0x100645de8 in FletX eval.c:936
> 
> There is a path from maybe_quit to redisplay, and didn't we have
> maybe_quit alreasy in the matcher code?  Mind-boggling!

Ouch!  This seems to be macOS-specific, though.

So I guess we should do this dance around calls to maybe_quit in
regex-emacs.c:

  specpdl_ref gc_count = inhibit_garbage_collection ();
  maybe_quit ();
  unbind_to (gc_count, Qnil);

Or maybe even better, do this inside probably_quit (because who knows
how many other callers of maybe_quit could be hit by this unexpected
GC)?

Can you try this?