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Re: Bug#751417: linux-image-3.2.0-4-5kc-malta: no SIGKILL after prctl(PR

To: Greg KH <greg@kroah.com>
Subject: Re: Bug#751417: linux-image-3.2.0-4-5kc-malta: no SIGKILL after prctl(PR_SET_SECCOMP, 1, ...) on MIPS
From: Ben Hutchings <ben@decadent.org.uk>
Date: Thu, 12 Jun 2014 22:10:59 +0100
Cc: stable <stable@vger.kernel.org>, linux-mips@linux-mips.org, Ralf Baechle <ralf@linux-mips.org>, 751417@bugs.debian.org, team@security.debian.org, Plamen Alexandrov <plamen@aomeda.com>, Markos Chandras <markos.chandras@imgtec.com>
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On Thu, 2014-06-12 at 14:05 -0700, Greg KH wrote:
> On Thu, Jun 12, 2014 at 02:03:23PM -0700, Greg KH wrote:
> > On Thu, Jun 12, 2014 at 09:21:41PM +0100, Ben Hutchings wrote:
> > > On Thu, 2014-06-12 at 20:36 +0100, Ben Hutchings wrote:
> > > > Control: tag -1 security upstream patch moreinfo
> > > > Control: severity -1 grave
> > > > Control: found -1 3.14.5-1
> > > 
> > > Aurelien Jarno pointed out this appears to be fixed upstream in 3.15:
> > > 
> > > commit 137f7df8cead00688524c82360930845396b8a21
> > > Author: Markos Chandras <markos.chandras@imgtec.com>
> > > Date:   Wed Jan 22 14:40:00 2014 +0000
> > > 
> > >     MIPS: asm: thread_info: Add _TIF_SECCOMP flag
> > > 
> > > It looks like this can be cherry-picked cleanly onto stable branches for
> > > 3.13 and 3.14.  For 3.11 and 3.12, it will need trivial adjustment.
> > > 
> > > For branches older than 3.11, this needs to be cherry-picked first:
> > > 
> > > commit e7f3b48af7be9f8007a224663a5b91340626fed5
> > > Author: Ralf Baechle <ralf@linux-mips.org>
> > > Date:   Wed May 29 01:02:18 2013 +0200
> > > 
> > >     MIPS: Cleanup flags in syscall flags handlers.
> > 
> > It also needs parts of 1d7bf993e0731b4ac790667c196b2a2d787f95c3 (MIPS:
> > ftrace: Add support for syscall tracepoints.) to apply properly to stuff
> > older than 3.11.  But, I'm not so sure that is good to apply as that is
> > a whole new feature.
> > 
> > So I think I'll just do this "by hand" to get it to work properly...
> 
> Wait, no, SECCOMP for MIPS isn't even in 3.10 or older kernels, so why
> is this a 3.2 issue?  Did you add it there to your kernel for some
> reason?

Seccomp mode 2 (i.e. filtering with BPF) was only just implenented for
MIPS in 3.15.  Mode 1 (fixed set of syscalls) was implemented long ago.

(If prctl(PR_SET_SECCOMP) could return success when CONFIG_SECCOMP is
not enabled, that would be even worse!)

Ben.

-- 
Ben Hutchings
The program is absolutely right; therefore, the computer must be wrong.

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