Messages in this thread | | | From | Andy Lutomirski <> | Date | Thu, 7 Nov 2013 10:16:13 -0800 | Subject | Re: [PATCH v2] seccomp: not compatible with ARM OABI |
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On Thu, Nov 7, 2013 at 9:47 AM, Kees Cook <keescook@chromium.org> wrote: > Make sure that seccomp filter won't be built when ARM OABI is in use, > since there is work needed to distinguish calling conventions. Until > that is done (which is likely never since OABI is deprecated), make > sure seccomp filter is unavailable in the OABI world. > > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > v2: > - toggle availability via HAVE_ARCH_SECCOMP_FILTER; James Hogan. > --- > arch/arm/Kconfig | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index 0a1dc697333c..a0a8590f3609 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -23,7 +23,7 @@ config ARM > select HARDIRQS_SW_RESEND > select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL > select HAVE_ARCH_KGDB > - select HAVE_ARCH_SECCOMP_FILTER > + select HAVE_ARCH_SECCOMP_FILTER if (AEABI && !OABI_COMPAT) > select HAVE_ARCH_TRACEHOOK > select HAVE_BPF_JIT > select HAVE_CONTEXT_TRACKING > @@ -1735,6 +1735,11 @@ config OABI_COMPAT > in memory differs between the legacy ABI and the new ARM EABI > (only for non "thumb" binaries). This option adds a tiny > overhead to all syscalls and produces a slightly larger kernel. > + > + The seccomp filter system will not be available when this is > + selected, since there is no way yet to sensibly distinguish > + between calling conventions during filtering. > + > If you know you'll be using only pure EABI user space then you > can say N here. If this option is not selected and you attempt > to execute a legacy ABI binary then the result will be > -- > 1.7.9.5 > >
FWIW, OABI-only (i.e. !AEABI, as opposed to OABI_COMPAT) is, in principle, supportable -- userspace would just have to know that, if build for OABI, the calling convention is different.
I doubt this is worth supporting, though, and, if no one complains about your patch for a couple releases, then that would mean we could get away with adding AUDIT_ARCH_ARM_OABI or something (maybe for seccomp only) if needed.
--Andy
> -- > Kees Cook > Chrome OS Security
-- Andy Lutomirski AMA Capital Management, LLC
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