> Date: Fri, 6 Jul 2018 15:05:56 +0300
> From: Paul Irofti <p...@irofti.net>
>
> Hi,
>
> The current implementation does not check for NULL attr values and
> segfaults when creating new threads if that's the case:
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x00000a77e9550ade in pthread_create (threadp=0x7f7ffffe5488,
> attr=0x7f7ffffe5480,
> start_routine=0xa7539a00600 <a_thread_func>, arg=<optimized out>) at
> /usr/src/lib/librthread/rthread.c:370
> 370 thread->attr = attr != NULL ? *(*attr) :
> _rthread_attr_default;
> (gdb) p attr
> $1 = (const pthread_attr_t *) 0x7f7ffffe5480
> (gdb) p *attr
> $2 = (const pthread_attr_t) 0x0
>
>
> The diff bellow fixes the issue by checking *attr and returning EINVAL
> if it is NULL. OK?
POSIX currently says:
The behavior is undefined if the value specified by the attr
argument to pthread_create() does not refer to an initialized thread
attributes object.
So your code is wrong and a segfault is perfectly fine behaviour. I
think our policy still is to crash as quickly as possible in the case
of undefined behaviour.
> (Surprisingly the manual already documents this.)
You mean:
[EINVAL] The value specified by attr is invalid.
? That isn't actually in the current version of POSIX, and I'm not
sure this covers a completely uninitialized attributes object.
So maybe we should change the man page instead?
> Index: rthread.c
> ===================================================================
> RCS file: /cvs/src/lib/librthread/rthread.c,v
> retrieving revision 1.99
> diff -u -p -u -p -r1.99 rthread.c
> --- rthread.c 4 Nov 2017 22:53:57 -0000 1.99
> +++ rthread.c 6 Jul 2018 12:04:07 -0000
> @@ -367,6 +367,9 @@ pthread_create(pthread_t *threadp, const
> thread->arg = arg;
> tib->tib_tid = -1;
>
> + if (attr != NULL && *attr == NULL)
> + return (EINVAL);
> +
> thread->attr = attr != NULL ? *(*attr) : _rthread_attr_default;
> if (thread->attr.sched_inherit == PTHREAD_INHERIT_SCHED) {
> pthread_t self = pthread_self();
>
>
