Re: [GIT PULL] security: seccomp changes for v4.21

[Kees Cook <keescook@chromium.org>]

On Mon, Jan 7, 2019 at 1:53 PM Tycho Andersen <tycho@tycho.ws> wrote:
>
> Hi,
>
> On Mon, Jan 07, 2019 at 01:09:09PM -0800, Kees Cook wrote:
> > On Mon, Jan 7, 2019 at 2:15 AM Ingo Molnar <mingo@kernel.org> wrote:
> > >
> > >
> > > * James Morris <jmorris@namei.org> wrote:
> > >
> > > > From Kees:
> > > >
> > > > "- Add SECCOMP_RET_USER_NOTIF
> > > >
> > > > - seccomp fixes for sparse warnings and s390 build (Tycho)"
> > > >
> > > >
> > > >
> > > > The following changes since commit 1072bd678547f8663cfb81a22fdb50c589e4976e:
> > > >
> > > >   security: fs: make inode explicitly non-modular (2018-12-12 14:58:51 -0800)
> > > >
> > > > are available in the Git repository at:
> > > >
> > > >   git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security.git next-seccomp
> > > >
> > > > for you to fetch changes up to 55b8cbe470d103b44104c64dbf89e5cad525d4e0:
> > > >
> > > >   Merge tag 'seccomp-next-part2' of https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux into next-seccomp (2018-12-17 11:36:26 -0800)
> > > >
> > > > ----------------------------------------------------------------
> > > > James Morris (2):
> > > >       Merge tag 'seccomp-next' of https://git.kernel.org/.../kees/linux into next-seccomp
> > > >       Merge tag 'seccomp-next-part2' of https://git.kernel.org/.../kees/linux into next-seccomp
> > > >
> > > > Tycho Andersen (6):
> > > >       seccomp: hoist struct seccomp_data recalculation higher
> > > >       seccomp: switch system call argument type to void *
> > > >       seccomp: add a return code to trap to userspace
> > > >       samples: add an example of seccomp user trap
> > > >       seccomp: fix poor type promotion
> > > >       seccomp, s390: fix build for syscall type change
> > > >
> > > >  Documentation/ioctl/ioctl-number.txt           |   1 +
> > > >  Documentation/userspace-api/seccomp_filter.rst |  84 +++++
> > > >  arch/s390/kernel/compat_wrapper.c              |   2 +-
> > > >  include/linux/seccomp.h                        |   9 +-
> > > >  include/linux/syscalls.h                       |   2 +-
> > > >  include/uapi/linux/seccomp.h                   |  40 ++-
> > > >  kernel/seccomp.c                               | 467 ++++++++++++++++++++++++-
> > > >  samples/seccomp/.gitignore                     |   1 +
> > > >  samples/seccomp/Makefile                       |   7 +-
> > > >  samples/seccomp/user-trap.c                    | 375 ++++++++++++++++++++
> > > >  tools/testing/selftests/seccomp/seccomp_bpf.c  | 447 ++++++++++++++++++++++-
> > > >  11 files changed, 1411 insertions(+), 24 deletions(-)
> > > >  create mode 100644 samples/seccomp/user-trap.c
> > >
> > > 32-bit x86 allyesconfig doesn't build:
> > >
> > >  /usr/bin/ld: i386:x86-64 architecture of input file `samples/seccomp/user-trap.o' is incompatible with i386 output
> > >  /usr/bin/ld: samples/seccomp/user-trap.o: file class ELFCLASS64 incompatible with ELFCLASS32
> > >  /usr/bin/ld: final link failed: File in wrong format
> > >  collect2: error: ld returned 1 exit status
> > >  scripts/Makefile.host:99: recipe for target 'samples/seccomp/user-trap' failed
> > >  make[2]: *** [samples/seccomp/user-trap] Error 1
> > >
> > > Is this a known regression?
> >
> > That looks like something is busted in the samples Makefile? Tycho,
> > are you able to reproduce this?
>
> Given that the samples build only happens when CROSS_COMPILE is not
> set, I'll see about digging up a 32-bit box. But I think the patch
> below should fix it, I'll send it out when I actually get it tested.

Cool, thanks for looking at it! :)

>
> Sorry for the breakage!
>
> Tycho
>
>
> From b53b390ab554ef6e5b995ac050718fd62ed0803e Mon Sep 17 00:00:00 2001
> From: Tycho Andersen <tycho@tycho.ws>
> Date: Mon, 7 Jan 2019 14:46:34 -0700
> Subject: [PATCH] samples/seccomp: fix 32-bit build
>
> Both the .o and the actual executable need to be built with -m32 in order
> to link correctly.
>
> Signed-off-by: Tycho Andersen <tycho@tycho.ws>

And just for tracking:

Fixes: fec7b6690541 ("samples: add an example of seccomp user trap")

Thanks!

-Kees

> Reported-by: Ingo Molnar <mingo@kernel.org>
> ---
>  samples/seccomp/Makefile | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/samples/seccomp/Makefile b/samples/seccomp/Makefile
> index 4920903c8009..a5607668a5c7 100644
> --- a/samples/seccomp/Makefile
> +++ b/samples/seccomp/Makefile
> @@ -37,6 +37,7 @@ HOSTCFLAGS_bpf-fancy.o += $(MFLAG)
>  HOSTLDLIBS_bpf-direct += $(MFLAG)
>  HOSTLDLIBS_bpf-fancy += $(MFLAG)
>  HOSTLDLIBS_dropper += $(MFLAG)
> +HOSTLDLIBS_user-trap.o += $(MFLAG)
>  HOSTLDLIBS_user-trap += $(MFLAG)
>  endif
>  always := $(hostprogs-m)
> --
> 2.19.1
>


-- 
Kees Cook