Date: Tue, 04 Nov 2003 19:49:03 +0000 From: Peter Edwards <peter.edwards@openet-telecom.com> To: David Schultz <das@FreeBSD.ORG> Cc: Igor Serikov <bt@turtle.freedns.us> Subject: Re: rfork problem Message-ID: <3FA802AF.4030107@openet-telecom.com> In-Reply-To: <20031104191526.GA79079@VARK.homeunix.com> References: <3FA61A17.70605@turtle.freedns.us> <20031104081800.GA78439@VARK.homeunix.com> <3FA76D43.1040508@turtle.freedns.us> <20031104191526.GA79079@VARK.homeunix.com>
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David Schultz wrote:
>On Tue, Nov 04, 2003, Igor Serikov wrote:
>
>
>> David,
>>
>>Is it okay to have a condition that can be created by a mortal user and
>>then cannot be changed by the root? The waiting process cannot be killed
>>and would keep "waiting" till system reboot.
>>
>>
>
>Aah, I see. No, it's not okay that a non-root user can create an
>unkillable process. -CURRENT doesn't have this problem because it
>rightly fails when a userland program tries to use RFPPWAIT. (It
>isn't supposed to be available to userland, which is why it isn't
>documented.) The problem could be fixed by backporting the
>relevant bits from -CURRENT.
>
>
>
>>I do not think it is a good idea to make ppwait state uninterruptible in
>>any case.
>>
>>
>
>I do not think it would be safe to deliver a signal to a parent
>process while a vforked child is borrowing its address space.
>
>Here's a patch against -STABLE:
>
>Index: kern_fork.c
>===================================================================
>RCS file: /cvs/src/sys/kern/kern_fork.c,v
>retrieving revision 1.72.2.15
>diff -u -r1.72.2.15 kern_fork.c
>--- kern_fork.c 28 Sep 2003 11:08:31 -0000 1.72.2.15
>+++ kern_fork.c 4 Nov 2003 19:13:33 -0000
>@@ -130,6 +130,9 @@
> int error;
> struct proc *p2;
>
>+ /* Don't allow kernel only flags. */
>+ if ((uap->flags & RFKERNELONLY) != 0)
>+ return (EINVAL);
> error = fork1(p, uap->flags, &p2);
> if (error == 0) {
> p->p_retval[0] = p2 ? p2->p_pid : 0;
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>
>
I don't think -STABLE defines RFKERNELONLY (or some of the other rfork
flags), so you need to add
Index: unistd.h
===================================================================
RCS file: /pub/FreeBSD/development/FreeBSD-CVS/src/sys/sys/unistd.h,v
retrieving revision 1.22.2.2
diff -u -r1.22.2.2 unistd.h
--- unistd.h 22 Aug 2000 01:46:30 -0000 1.22.2.2
+++ unistd.h 4 Nov 2003 19:46:03 -0000
@@ -218,6 +218,7 @@
#define RFSIGSHARE (1<<14) /* share signal handlers */
#define RFLINUXTHPN (1<<16) /* do linux clone exit parent
notification */
#define RFPPWAIT (1<<31) /* parent sleeps until child exits
(vfork) */
+#define RFKERNELONLY RFPPWAIT
#endif /* !_POSIX_SOURCE */
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