Re: [Qemu-devel] seccomp breakage on arm

[Paul Moore <pmoore@redhat.com>]

On Thursday, April 09, 2015 11:32:51 PM Peter Maydell wrote:
> On 9 April 2015 at 22:27, Paul Moore <pmoore@redhat.com> wrote:
> > Regardless, I think I see what the problem is, and if I'm correct it
> > affects time, umount, stime, alarm, utime, getrlimit, select, readdir,
> > mmap, socketcall, syscall, and ipc.  I'm traveling at the moment so a
> > patch may be a bit delayed, but I'll be sure to CC you on the fix in case
> > you are able to do some testing.
> 
> I was expecting seccomp 2.2.x to fix this by not requiring the
> existence in particular of *any* __NR_* define.

I'm sorry to tell you that it doesn't work that way.

> If you don't make the header cope with any of them being missing then this
> is going to continue to be fragile and liable to breakage on new
> architectures into the future, I suspect :-(

There are always going to be teething problems with support for new 
architectures, especially ones that I do not personally have in front of me 
for testing.  Due to the nature of syscall filtering and the libseccomp API, 
the libseccomp library needs to maintain its own list of syscalls for each 
architecture/ABI; while this list is fairly static and doesn't often change, 
there are situations (e.g. adding a new ABI) that cause significant change and 
take some time to sort out.  If you feel that you have a better design for 
libseccomp you are always welcome to submit patches, I'm happy to review code.

I can't promise you there won't ever be bugs, but I think I've demonstrated 
that we take these things seriously and address the issues as we are made 
aware of them.  Surely libseccomp isn't the only project to have bugs ;)

> For the moment I think we should revert the "2.2 is OK on
> ARM" QEMU configure patch for QEMU's 2.3 release, and go
> back to the status-quo of "assume this only works on x86".

The QEMU developers can do whatever they feel is best for the project; my main 
concern is maintaining libseccomp.

-- 
paul moore
security @ redhat