On Wed, Dec 23, 2020 at 11:58:30PM -0700, Theo de Raadt wrote:
> Brad Smith <[email protected]> wrote:
>
> > On 12/23/2020 10:35 PM, Alexey Sokolov wrote:
> > >> Synopsis: getaddrinfo() is not thread-safe in 6.8
> > >> Category: system
> > >> Environment:
> > > System : OpenBSD 6.8
> > > Details : OpenBSD 6.8 (GENERIC.MP) #1: Tue Nov 3 09:06:04 MST 2020
> > >
> > > [email protected]:/usr/src/sys/arch/amd64/compile/GENERIC.MP
> > >
> > > Architecture: OpenBSD.amd64
> > > Machine : amd64
> > >> Description:
> > > Hi, getaddrinfo() crashes when multiple threads run getaddrinfo()
> > > concurrently. This didn't happen in 6.7.
> > > It looks like asr_ctx which is supposed to be thread-local according to
> > > _asr_use_resolver(), is actually static / shared between threads.
> > >> How-To-Repeat:
> > > Compile this code (gcc a.c -pthread), and run. It will segfault in
> > > several seconds. Happens with both gcc (4.2.1) and egcc (8.4.0).
> >
> > Before going any further. Use the system compiler. That is Clang (cc).
>
> I disagree. As the test appears fairly idiomatic threading code, I
> find it unlikely a compiler change should matter.
FWIW I compiled psychon's code with clang (cc) with cc -g -o threadtest \
threadtest.c -lpthread
and got this:
pjp@arda$ ./threadtest
Segmentation fault (core dumped)
pjp@arda$ gdb ./threadtest threadtest.core
...
#0 0x00000f22d59c228c in getaddrinfo_async_run (as=0xf229d095000, ar=Variable "
ar" is not available)
at /usr/src/lib/libc/asr/getaddrinfo_async.c:513
513 return AS_FAMILY(as);
(gdb) print *as
...
is->as_family_idx
$2 = 34
(gdb) where
#0 0x00000f22d59c228c in getaddrinfo_async_run (as=0xf229d095000, ar=Variable "
ar" is not available.
)
at /usr/src/lib/libc/asr/getaddrinfo_async.c:513
#1 0x00000f22d59ba4d7 in _libc_asr_run_sync (as=0xf229d095000,
ar=0x7f7ffffe8448) at /usr/src/lib/libc/asr/asr.c:178
#2 0x00000f22d599e008 in _libc_getaddrinfo (
hostname=0xf201c7ce6b8 "ipv4.google.com", servname=0x0,
...
(gdb) info threads
* 1 process 608275 0x00000f22d59c228c in getaddrinfo_async_run (
as=0xf229d095000, ar=Variable "ar" is not available.
) at /usr/src/lib/libc/asr/getaddrinfo_async.c:513
...
This means that the other 4 threads exited by now, here is my system's
kern.version:
kern.version=OpenBSD 6.8 (GENERIC.MP) #2: Sat Dec 5 07:17:48 MST 2020
[email protected]:/usr/src/sys/arch/amd64/compile/GENERIC.MP
latest smtpd patch not on it (yet)...
Best Regards,
-peter
