Date: Sat, 16 Jan 2016 14:08:58 -0800 From: Vijay Singh <vijju.singh@gmail.com> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Chagin Dmitry <dchagin@freebsd.org>, freebsd-hackers@freebsd.org Subject: Re: irrelevant locking Message-ID: <CALCNsJT_gH5gJaB%2ByVQRcON84JntSUevG8-X-0Z5_13DkPC%2BBg@mail.gmail.com> In-Reply-To: <20160116202643.GL3942@kib.kiev.ua> References: <20160116195819.GA41610@chd.heemeyer.club> <20160116202643.GL3942@kib.kiev.ua>
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Couldn't the get & set race otherwise?
On Jan 16, 2016 12:27 PM, "Konstantin Belousov" <kostikbel@gmail.com> wrote:
> On Sat, Jan 16, 2016 at 10:58:19PM +0300, Chagin Dmitry wrote:
> > hi, please, can someone explain the reason to take the process lock here:
> There is no reason, I think that the PROC_LOCK() can be removed.
>
> >
> > int
> > sys_issetugid(register struct thread *td, struct issetugid_args *uap)
> > {
> > struct proc *p = td->td_proc;
> >
> > /*
> > * Note: OpenBSD sets a P_SUGIDEXEC flag set at execve() time,
> > * we use P_SUGID because we consider changing the owners as
> > * "tainting" as well.
> > * This is significant for procs that start as root and "become"
> > * a user without an exec - programs cannot know *everything*
> > * that libc *might* have put in their data segment.
> > */
> > PROC_LOCK(p);
> > td->td_retval[0] = (p->p_flag & P_SUGID) ? 1 : 0;
> > PROC_UNLOCK(p);
> > return (0);
> > }
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