GNU bug report logs - #42530
28.0.50; Integer overflows in alloc.c on macOS

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Philipp <p.stephani2 <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 28.0.50; Integer overflows in alloc.c on macOS
Date: Sat, 25 Jul 2020 19:20:07 +0200

-fsanitize=undefined finds the following integer overflows in alloc.c:

alloc.c:4641:33: runtime error: addition of unsigned offset to 0x000102496c05 overflowed to 0x000102496c00
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior alloc.c:4641:33 in 
alloc.c:4852:9: runtime error: pointer index expression with base 0xffffffffffffffff overflowed to 0x00010344053f
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior alloc.c:4852:9 in 

I briefly checked the code, but couldn't find anything obviously wrong.
Note that UBSan also checks for unsigned integer overflows, which are
technically not undefined, but might still be fishy.  If these overflows
are intended, we should probably use INT_ADD_WRAPV to make that clear
and suppress the sanitizer.


In GNU Emacs 28.0.50 (build 66, x86_64-apple-darwin19.5.0, NS appkit-1894.50 Version 10.15.5 (Build 19F101))
 of 2020-07-25
Repository revision: 3b44829823f43d3736b8ec9db2258eeff7f6c16a
Repository branch: master
Windowing system distributor 'Apple', version 10.3.1894
System Description:  Mac OS X 10.15.5

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --with-modules --without-xml2 --without-pop --with-mailutils
 --enable-gcc-warnings=warn-only --enable-checking=all
 --enable-check-lisp-object-type 'CFLAGS=-g3 -O1 -fsanitize=address
 -fsanitize=undefined -fno-omit-frame-pointer''

Configured features:
JPEG TIFF GIF PNG NOTIFY KQUEUE ACL GNUTLS ZLIB TOOLKIT_SCROLL_BARS NS
MODULES THREADS JSON PDUMPER LCMS2

Important settings:
  value of $LANG: de_DE.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
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  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
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  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

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Memory information:
((conses 16 69705 5415)
 (symbols 48 8650 1)
 (strings 32 23527 1769)
 (string-bytes 1 768093)
 (vectors 16 14130)
 (vector-slots 8 172256 4253)
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Message #8 received at 42530 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Philipp <p.stephani2 <at> gmail.com>
Cc: 42530 <at> debbugs.gnu.org
Subject: Re: bug#42530: 28.0.50; Integer overflows in alloc.c on macOS
Date: Sat, 17 Oct 2020 11:05:55 +0200

Philipp <p.stephani2 <at> gmail.com> writes:

> -fsanitize=undefined finds the following integer overflows in alloc.c:
>
> alloc.c:4641:33: runtime error: addition of unsigned offset to 0x000102496c05 overflowed to 0x000102496c00
> SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior alloc.c:4641:33 in 
> alloc.c:4852:9: runtime error: pointer index expression with base 0xffffffffffffffff overflowed to 0x00010344053f
> SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior alloc.c:4852:9 in 

How do you reproduce this?  I tried

./configure CFLAGS='-g3 -O1 -fsanitize=address -fsanitize=undefined -fno-omit-frame-pointer' --with-modules --without-xml2 --without-pop --with-mailutils --enable-gcc-warnings=warn-only --enable-checking=all --enable-check-lisp-object-type 

and then started Emacs (on Catalina), but didn't get any errors as far
as I can see.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #11 received at 42530 <at> debbugs.gnu.org (full text, mbox):

From: Philipp Stephani <p.stephani2 <at> gmail.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 42530 <at> debbugs.gnu.org
Subject: Re: bug#42530: 28.0.50; Integer overflows in alloc.c on macOS
Date: Sat, 17 Oct 2020 14:12:03 +0200

Am Sa., 17. Okt. 2020 um 11:06 Uhr schrieb Lars Ingebrigtsen <larsi <at> gnus.org>:
>
> Philipp <p.stephani2 <at> gmail.com> writes:
>
> > -fsanitize=undefined finds the following integer overflows in alloc.c:
> >
> > alloc.c:4641:33: runtime error: addition of unsigned offset to 0x000102496c05 overflowed to 0x000102496c00
> > SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior alloc.c:4641:33 in
> > alloc.c:4852:9: runtime error: pointer index expression with base 0xffffffffffffffff overflowed to 0x00010344053f
> > SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior alloc.c:4852:9 in
>
> How do you reproduce this?  I tried
>
> ./configure CFLAGS='-g3 -O1 -fsanitize=address -fsanitize=undefined -fno-omit-frame-pointer' --with-modules --without-xml2 --without-pop --with-mailutils --enable-gcc-warnings=warn-only --enable-checking=all --enable-check-lisp-object-type
>
> and then started Emacs (on Catalina), but didn't get any errors as far
> as I can see.

According to 'git bisect' this was fixed by

commit 069b58b7c852b59f8ef7642e21db339626045671
Author: Philipp Stephani <phst <at> google.com>
Date:   Sun Aug 2 12:58:44 2020 +0200

    * src/alloc.c (mark_memory): Avoid signed integer overflow

 src/alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

and probably other commits around that time.

Message #14 received at 42530 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Philipp Stephani <p.stephani2 <at> gmail.com>
Cc: 42530 <at> debbugs.gnu.org
Subject: Re: bug#42530: 28.0.50; Integer overflows in alloc.c on macOS
Date: Sun, 18 Oct 2020 10:15:26 +0200

Philipp Stephani <p.stephani2 <at> gmail.com> writes:

> According to 'git bisect' this was fixed by
>
> commit 069b58b7c852b59f8ef7642e21db339626045671
> Author: Philipp Stephani <phst <at> google.com>
> Date:   Sun Aug 2 12:58:44 2020 +0200
>
>     * src/alloc.c (mark_memory): Avoid signed integer overflow
>
>  src/alloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> and probably other commits around that time.

Thanks; I'm closing this bug report, then.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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