Recent libX11 update broke emacs

[Niclas Zeising]

On 2020-08-04 06:48, Ashish SHUKLA wrote:
> On 8/4/20 10:04 AM, Ashish SHUKLA wrote:
>> On 8/4/20 3:38 AM, Niclas Zeising wrote:
>>> On 2020-08-03 19:07, Kevin Oberman wrote:
>>>> This is a weird problem and I'm uncertain if it is in libW11,
> x11-server,
>>>> or emacs. As a result, I'm crossposting to both lists.
>>>>
>>>> Yesterday, after upgrading libX11 and x11-server, I could no longer run
>>>> Emacs to an  X display. It crashed quickly with a segmentation error
>>>> in the
>>>> pthread library. Oddly, I could run it to my local xserver from a remote
>>>> system.
>>>
>>> Where does the segfault occur before entering pthreads?
>>>
>>>> Rolling back the x11 server did not help nor did rolling back libX11 or
>>>> even both of them. I had to roll back libX11 first and build the server
>>>> with the old libX11. Rebuilding emacs with the new ports made no
>>>> difference.
>>>
>>> Which version of the server did you build?  The patch to xorg-server is
>>> trivial, just switching out malloc for calloc have the memory 0
>>> initialized.  The patch to libX11 is rather more involved.
>>> It is possible that someone accidentally changed the ABI of libX11, I
>>> guess.  What happens if you use the version with just the security fixes
>>> (the version I committed first, and that was merged to the Q3 branch.)
>>>
>>>>
>>>> Since the old libX11 contains a very serious vulnerability, I  really
>>>> hate
>>>> to leave it this way, but I also have a hard time getting anything done
>>>> without emacs. Nothing other than emacs seems to have a problem with
> this
>>>
>>> There is one commit after libX11 1.6.10, that takes care of a regression.
>>> Can you apply
>>>
> https://gitlab.freedesktop.org/xorg/lib/libx11/-/commit/93fce3f4e79cbc737d6468a4f68ba3de1b83953b
>>> on top of the libX11 1.6.10 update and see if that fixes anything?
>>>
>>> Regards
>>
>> Able to get Emacs to segfault:
>>
>> λ lldb -e /usr/local/bin/emacs
>> (lldb) target create "/usr/local/bin/emacs"
>> Current executable set to '/usr/local/bin/emacs' (x86_64).
>> (lldb) run -Q
>> Process 36196 launching
>> Process 36196 launched: '/usr/local/bin/emacs' (x86_64)
>> Process 36196 stopped
>> * thread #1, name = 'emacs-28.0.50', stop reason = signal SIGSEGV:
>> invalid address (fault address: 0x0)
>>      frame #0: 0x0000000000427ca0
>> emacs`best_xim_style(xim=0x0000000000000000) at xfns.c:2629:21
>> (lldb) bt
> [...]
> 
>>
>>
>> And workaround is launching Emacs like: env -u XMODIFIERS emacs
>>
>> I'll try the libX11 patch and give it a shot.
> 
> Emacs, with libX11 built with the patch, works fine now. It seems like
> it's also reported in Debian[1], and they merged it. Maybe we can do the
> same ?
> 
> References:
> [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=966691
> 

Thank you, I'll see about adding that patch to the port and package then.
It looks like this is both a bug in libX11 and to some extent also emacs?

Kevin, can you double check that the patch works for you.  I find it 
strange that you have to rebuild both xorg-server and libX11 for it to 
work, are you forcing static linkage somewhere?
Regards
-- 
Niclas