Re: [PATCH 2/2] RISC-V: Add support for SECCOMP

On Wed, Oct 24, 2018 at 2:42 PM Kees Cook <keescook(a)chromium.org&gt; wrote: > > On Wed, Oct 24, 2018 at 1:40 PM, Palmer Dabbelt <palmer(a)sifive.com&gt; wrote: > > From: "Wesley W. Terpstra" <wesley(a)sifive.com&gt; > > > > This is a fairly straight-forward implementation of seccomp for RISC-V > > systems. > > > > Signed-off-by: Wesley W. Terpstra <wesley(a)sifive.com&gt; > > Signed-off-by: Palmer Dabbelt <palmer(a)sifive.com&gt; > > --- > > arch/riscv/Kconfig | 18 ++++++++++++++++++ > > arch/riscv/include/asm/seccomp.h | 10 ++++++++++ > > arch/riscv/include/asm/syscall.h | 6 ++++++ > > arch/riscv/include/asm/thread_info.h | 1 + > > include/uapi/linux/audit.h | 1 + > > 5 files changed, 36 insertions(+) > > create mode 100644 arch/riscv/include/asm/seccomp.h > > > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > > index a344980287a5..28abe47602a1 100644 > > --- a/arch/riscv/Kconfig > > +++ b/arch/riscv/Kconfig > > @@ -28,6 +28,7 @@ config RISCV > > select GENERIC_STRNLEN_USER > > select GENERIC_SMP_IDLE_THREAD > > select GENERIC_ATOMIC64 if !64BIT || !RISCV_ISA_A > > + select HAVE_ARCH_SECCOMP_FILTER > > I think this patch is missing most of the actual seccomp glue? > > config HAVE_ARCH_SECCOMP_FILTER > bool > help > An arch should select this symbol if it provides all of these things: > - syscall_get_arch() > - syscall_get_arguments() > - syscall_rollback() > - syscall_set_return_value() > - SIGSYS siginfo_t support > - secure_computing is called from a ptrace_event()-safe context > - secure_computing return value is checked and a return value of -1 > results in the system call being skipped immediately. > - seccomp syscall wired up > > I only see syscall_get_arch(). Nothing is using TIF_SECCOMP (I'd > expect a masked check in entry.S -- it seems like tracepoints are > getting missed too? I see it handled in ptrace.c but not checked in > entry.S?) There's no checking for seccomp in ptrace.c, etc. Hi RISC-V people: I strongly, strongly suggest that you rewrite your asm to work the way that x86's does: have a function called prepare_exit_to_usermode() and make it work more or less like x86's. Doing all the exit work in asm like you are is just setting you up for a world of pain.