Re: Bug#751417: linux-image-3.2.0-4-5kc-malta: no SIGKILL after prctl(PR_SET_SECCOMP, 1, ...) on MIPS

[Greg KH <greg@kroah.com>]

On Thu, Jun 12, 2014 at 10:10:59PM +0100, Ben Hutchings wrote:
> 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.

Really?  I don't see _TIF_SECCOMP in the mips asm files in 3.10.  I
don't feel comfortable backporting it to 3.10 or 3.4, are you going to
do that for 3.2?

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

True, but this seems to have always been broken, right?  :)

thanks,

greg k-h