On Thu, Nov 7, 2013 at 10:16 AM, Andy Lutomirski <[email protected]> wrote: > On Thu, Nov 7, 2013 at 9:47 AM, Kees Cook <[email protected]> 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 <[email protected]> >> --- >> 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.
Right -- I opted for enforcing seccomp-on-ARM-means-EABI. > 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. Agreed. Thanks again for looking at all this! -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
