Re: [PATCH v2] riscv: add support for SECCOMP and SECCOMP_FILTER

From: Carlos Eduardo de Paula
Date: Fri Aug 23 2019 - 19:01:55 EST

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On Thu, Aug 22, 2019 at 5:56 PM David Abdurachmanov
<david.abdurachmanov@xxxxxxxxx> wrote:
>
> This patch was extensively tested on Fedora/RISCV (applied by default on
> top of 5.2-rc7 kernel for <2 months). The patch was also tested with 5.3-rc
> on QEMU and SiFive Unleashed board.
>
> libseccomp (userspace) was rebased:
> https://github.com/seccomp/libseccomp/pull/134
>
> Fully passes libseccomp regression testing (simulation and live).
>
> There is one failing kernel selftest: global.user_notification_signal
>
> v1 -> v2:
> - return immediatly if secure_computing(NULL) returns -1
> - fixed whitespace issues
> - add missing seccomp.h
> - remove patch #2 (solved now)
> - add riscv to seccomp kernel selftest
>
> Cc: keescook@xxxxxxxxxxxx
> Cc: me@xxxxxxxxxxxxx
>
> Signed-off-by: David Abdurachmanov <david.abdurachmanov@xxxxxxxxxx>
> Tested-by: Carlos de Paula <me@xxxxxxxxxxxxx>
> ---
> arch/riscv/Kconfig | 14 ++++++++++
> arch/riscv/include/asm/seccomp.h | 10 +++++++
> arch/riscv/include/asm/thread_info.h | 5 +++-
> arch/riscv/kernel/entry.S | 27 +++++++++++++++++--
> arch/riscv/kernel/ptrace.c | 10 +++++++
> tools/testing/selftests/seccomp/seccomp_bpf.c | 8 +++++-
> 6 files changed, 70 insertions(+), 4 deletions(-)
> create mode 100644 arch/riscv/include/asm/seccomp.h
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 59a4727ecd6c..441e63ff5adc 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -31,6 +31,7 @@ config RISCV
> select GENERIC_SMP_IDLE_THREAD
> select GENERIC_ATOMIC64 if !64BIT
> select HAVE_ARCH_AUDITSYSCALL
> + select HAVE_ARCH_SECCOMP_FILTER
> select HAVE_MEMBLOCK_NODE_MAP
> select HAVE_DMA_CONTIGUOUS
> select HAVE_FUTEX_CMPXCHG if FUTEX
> @@ -235,6 +236,19 @@ menu "Kernel features"
>
> source "kernel/Kconfig.hz"
>
> +config SECCOMP
> + bool "Enable seccomp to safely compute untrusted bytecode"
> + help
> + This kernel feature is useful for number crunching applications
> + that may need to compute untrusted bytecode during their
> + execution. By using pipes or other transports made available to
> + the process as file descriptors supporting the read/write
> + syscalls, it's possible to isolate those applications in
> + their own address space using seccomp. Once seccomp is
> + enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
> + and the task is only allowed to execute a few safe syscalls
> + defined by each seccomp mode.
> +
> endmenu
>
> menu "Boot options"
> diff --git a/arch/riscv/include/asm/seccomp.h b/arch/riscv/include/asm/seccomp.h
> new file mode 100644
> index 000000000000..bf7744ee3b3d
> --- /dev/null
> +++ b/arch/riscv/include/asm/seccomp.h
> @@ -0,0 +1,10 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef _ASM_SECCOMP_H
> +#define _ASM_SECCOMP_H
> +
> +#include <asm/unistd.h>
> +
> +#include <asm-generic/seccomp.h>
> +
> +#endif /* _ASM_SECCOMP_H */
> diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
> index 905372d7eeb8..a0b2a29a0da1 100644
> --- a/arch/riscv/include/asm/thread_info.h
> +++ b/arch/riscv/include/asm/thread_info.h
> @@ -75,6 +75,7 @@ struct thread_info {
> #define TIF_MEMDIE 5 /* is terminating due to OOM killer */
> #define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */
> #define TIF_SYSCALL_AUDIT 7 /* syscall auditing */
> +#define TIF_SECCOMP 8 /* syscall secure computing */
>
> #define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
> #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
> @@ -82,11 +83,13 @@ struct thread_info {
> #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
> #define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT)
> #define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
> +#define _TIF_SECCOMP (1 << TIF_SECCOMP)
>
> #define _TIF_WORK_MASK \
> (_TIF_NOTIFY_RESUME | _TIF_SIGPENDING | _TIF_NEED_RESCHED)
>
> #define _TIF_SYSCALL_WORK \
> - (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_AUDIT)
> + (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_AUDIT | \
> + _TIF_SECCOMP )
>
> #endif /* _ASM_RISCV_THREAD_INFO_H */
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index bc7a56e1ca6f..0bbedfa3e47d 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -203,8 +203,25 @@ check_syscall_nr:
> /* Check to make sure we don't jump to a bogus syscall number. */
> li t0, __NR_syscalls
> la s0, sys_ni_syscall
> - /* Syscall number held in a7 */
> - bgeu a7, t0, 1f
> + /*
> + * The tracer can change syscall number to valid/invalid value.
> + * We use syscall_set_nr helper in syscall_trace_enter thus we
> + * cannot trust the current value in a7 and have to reload from
> + * the current task pt_regs.
> + */
> + REG_L a7, PT_A7(sp)
> + /*
> + * Syscall number held in a7.
> + * If syscall number is above allowed value, redirect to ni_syscall.
> + */
> + bge a7, t0, 1f
> + /*
> + * Check if syscall is rejected by tracer or seccomp, i.e., a7 == -1.
> + * If yes, we pretend it was executed.
> + */
> + li t1, -1
> + beq a7, t1, ret_from_syscall_rejected
> + /* Call syscall */
> la s0, sys_call_table
> slli t0, a7, RISCV_LGPTR
> add s0, s0, t0
> @@ -215,6 +232,12 @@ check_syscall_nr:
> ret_from_syscall:
> /* Set user a0 to kernel a0 */
> REG_S a0, PT_A0(sp)
> + /*
> + * We didn't execute the actual syscall.
> + * Seccomp already set return value for the current task pt_regs.
> + * (If it was configured with SECCOMP_RET_ERRNO/TRACE)
> + */
> +ret_from_syscall_rejected:
> /* Trace syscalls, but only if requested by the user. */
> REG_L t0, TASK_TI_FLAGS(tp)
> andi t0, t0, _TIF_SYSCALL_WORK
> diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
> index 368751438366..63e47c9f85f0 100644
> --- a/arch/riscv/kernel/ptrace.c
> +++ b/arch/riscv/kernel/ptrace.c
> @@ -154,6 +154,16 @@ void do_syscall_trace_enter(struct pt_regs *regs)
> if (tracehook_report_syscall_entry(regs))
> syscall_set_nr(current, regs, -1);
>
> + /*
> + * Do the secure computing after ptrace; failures should be fast.
> + * If this fails we might have return value in a0 from seccomp
> + * (via SECCOMP_RET_ERRNO/TRACE).
> + */
> + if (secure_computing(NULL) == -1) {
> + syscall_set_nr(current, regs, -1);
> + return;
> + }
> +
> #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
> if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
> trace_sys_enter(regs, syscall_get_nr(current, regs));
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index 6ef7f16c4cf5..492e0adad9d3 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -112,6 +112,8 @@ struct seccomp_data {
> # define __NR_seccomp 383
> # elif defined(__aarch64__)
> # define __NR_seccomp 277
> +# elif defined(__riscv)
> +# define __NR_seccomp 277
> # elif defined(__hppa__)
> # define __NR_seccomp 338
> # elif defined(__powerpc__)
> @@ -1582,6 +1584,10 @@ TEST_F(TRACE_poke, getpid_runs_normally)
> # define ARCH_REGS struct user_pt_regs
> # define SYSCALL_NUM regs[8]
> # define SYSCALL_RET regs[0]
> +#elif defined(__riscv) && __riscv_xlen == 64
> +# define ARCH_REGS struct user_regs_struct
> +# define SYSCALL_NUM a7
> +# define SYSCALL_RET a0
> #elif defined(__hppa__)
> # define ARCH_REGS struct user_regs_struct
> # define SYSCALL_NUM gr[20]
> @@ -1671,7 +1677,7 @@ void change_syscall(struct __test_metadata *_metadata,
> EXPECT_EQ(0, ret) {}
>
> #if defined(__x86_64__) || defined(__i386__) || defined(__powerpc__) || \
> - defined(__s390__) || defined(__hppa__)
> + defined(__s390__) || defined(__hppa__) || defined(__riscv)
> {
> regs.SYSCALL_NUM = syscall;
> }
> --
> 2.21.0
>

Kernel selftests results:

â uname -a
Linux fedora-unleashed 5.2.0-rc7-30159-g2d072d4-dirty #3 SMP Thu Jul 4
20:18:21 -03 2019 riscv64 riscv64 riscv64 GNU/Linux

â sudo ./seccomp_bpf
[==========] Running 74 tests from 1 test cases.
[ RUN ] global.mode_strict_support
[ OK ] global.mode_strict_support
[ RUN ] global.mode_strict_cannot_call_prctl
[ OK ] global.mode_strict_cannot_call_prctl
[ RUN ] global.no_new_privs_support
[ OK ] global.no_new_privs_support
[ RUN ] global.mode_filter_support
[ OK ] global.mode_filter_support
[ RUN ] global.mode_filter_without_nnp
[ OK ] global.mode_filter_without_nnp
[ RUN ] global.filter_size_limits
[ OK ] global.filter_size_limits
[ RUN ] global.filter_chain_limits
[ OK ] global.filter_chain_limits
[ RUN ] global.mode_filter_cannot_move_to_strict
[ OK ] global.mode_filter_cannot_move_to_strict
[ RUN ] global.mode_filter_get_seccomp
[ OK ] global.mode_filter_get_seccomp
[ RUN ] global.ALLOW_all
[ OK ] global.ALLOW_all
[ RUN ] global.empty_prog
[ OK ] global.empty_prog
[ RUN ] global.log_all
[ OK ] global.log_all
[ RUN ] global.unknown_ret_is_kill_inside
[ OK ] global.unknown_ret_is_kill_inside
[ RUN ] global.unknown_ret_is_kill_above_allow
[ OK ] global.unknown_ret_is_kill_above_allow
[ RUN ] global.KILL_all
[ OK ] global.KILL_all
[ RUN ] global.KILL_one
[ OK ] global.KILL_one
[ RUN ] global.KILL_one_arg_one
[ OK ] global.KILL_one_arg_one
[ RUN ] global.KILL_one_arg_six
[ OK ] global.KILL_one_arg_six
[ RUN ] global.KILL_thread
[ OK ] global.KILL_thread
[ RUN ] global.KILL_process
[ OK ] global.KILL_process
[ RUN ] global.arg_out_of_range
[ OK ] global.arg_out_of_range
[ RUN ] global.ERRNO_valid
[ OK ] global.ERRNO_valid
[ RUN ] global.ERRNO_zero
[ OK ] global.ERRNO_zero
[ RUN ] global.ERRNO_capped
[ OK ] global.ERRNO_capped
[ RUN ] global.ERRNO_order
[ OK ] global.ERRNO_order
[ RUN ] TRAP.dfl
[ OK ] TRAP.dfl
[ RUN ] TRAP.ign
[ OK ] TRAP.ign
[ RUN ] TRAP.handler
[ OK ] TRAP.handler
[ RUN ] precedence.allow_ok
[ OK ] precedence.allow_ok
[ RUN ] precedence.kill_is_highest
[ OK ] precedence.kill_is_highest
[ RUN ] precedence.kill_is_highest_in_any_order
[ OK ] precedence.kill_is_highest_in_any_order
[ RUN ] precedence.trap_is_second
[ OK ] precedence.trap_is_second
[ RUN ] precedence.trap_is_second_in_any_order
[ OK ] precedence.trap_is_second_in_any_order
[ RUN ] precedence.errno_is_third
[ OK ] precedence.errno_is_third
[ RUN ] precedence.errno_is_third_in_any_order
[ OK ] precedence.errno_is_third_in_any_order
[ RUN ] precedence.trace_is_fourth
[ OK ] precedence.trace_is_fourth
[ RUN ] precedence.trace_is_fourth_in_any_order
[ OK ] precedence.trace_is_fourth_in_any_order
[ RUN ] precedence.log_is_fifth
[ OK ] precedence.log_is_fifth
[ RUN ] precedence.log_is_fifth_in_any_order
[ OK ] precedence.log_is_fifth_in_any_order
[ RUN ] TRACE_poke.read_has_side_effects
[ OK ] TRACE_poke.read_has_side_effects
[ RUN ] TRACE_poke.getpid_runs_normally
[ OK ] TRACE_poke.getpid_runs_normally
[ RUN ] TRACE_syscall.ptrace_syscall_redirected
[ OK ] TRACE_syscall.ptrace_syscall_redirected
[ RUN ] TRACE_syscall.ptrace_syscall_errno
[ OK ] TRACE_syscall.ptrace_syscall_errno
[ RUN ] TRACE_syscall.ptrace_syscall_faked
[ OK ] TRACE_syscall.ptrace_syscall_faked
[ RUN ] TRACE_syscall.syscall_allowed
[ OK ] TRACE_syscall.syscall_allowed
[ RUN ] TRACE_syscall.syscall_redirected
[ OK ] TRACE_syscall.syscall_redirected
[ RUN ] TRACE_syscall.syscall_errno
[ OK ] TRACE_syscall.syscall_errno
[ RUN ] TRACE_syscall.syscall_faked
[ OK ] TRACE_syscall.syscall_faked
[ RUN ] TRACE_syscall.skip_after_RET_TRACE
[ OK ] TRACE_syscall.skip_after_RET_TRACE
[ RUN ] TRACE_syscall.kill_after_RET_TRACE
[ OK ] TRACE_syscall.kill_after_RET_TRACE
[ RUN ] TRACE_syscall.skip_after_ptrace
[ OK ] TRACE_syscall.skip_after_ptrace
[ RUN ] TRACE_syscall.kill_after_ptrace
[ OK ] TRACE_syscall.kill_after_ptrace
[ RUN ] global.seccomp_syscall
[ OK ] global.seccomp_syscall
[ RUN ] global.seccomp_syscall_mode_lock
[ OK ] global.seccomp_syscall_mode_lock
[ RUN ] global.detect_seccomp_filter_flags
[ OK ] global.detect_seccomp_filter_flags
[ RUN ] global.TSYNC_first
[ OK ] global.TSYNC_first
[ RUN ] TSYNC.siblings_fail_prctl
[ OK ] TSYNC.siblings_fail_prctl
[ RUN ] TSYNC.two_siblings_with_ancestor
[ OK ] TSYNC.two_siblings_with_ancestor
[ RUN ] TSYNC.two_sibling_want_nnp
[ OK ] TSYNC.two_sibling_want_nnp
[ RUN ] TSYNC.two_siblings_with_no_filter
[ OK ] TSYNC.two_siblings_with_no_filter
[ RUN ] TSYNC.two_siblings_with_one_divergence
[ OK ] TSYNC.two_siblings_with_one_divergence
[ RUN ] TSYNC.two_siblings_not_under_filter
[ OK ] TSYNC.two_siblings_not_under_filter
[ RUN ] global.syscall_restart
[ OK ] global.syscall_restart
[ RUN ] global.filter_flag_log
[ OK ] global.filter_flag_log
[ RUN ] global.get_action_avail
[ OK ] global.get_action_avail
[ RUN ] global.get_metadata
[ OK ] global.get_metadata
[ RUN ] global.user_notification_basic
[ OK ] global.user_notification_basic
[ RUN ] global.user_notification_kill_in_middle
[ OK ] global.user_notification_kill_in_middle
[ RUN ] global.user_notification_signal
[1] 5951 alarm sudo ./seccomp_bpf

carlosedp in ~ at fedora-unleashed
â sudo ./seccomp_benchmark
Calibrating reasonable sample size...
1564584448.964538790 - 1564584448.964529687 = 9103
1564584448.964588859 - 1564584448.964575204 = 13655
1564584448.964631342 - 1564584448.964604790 = 26552
1564584448.964710239 - 1564584448.964644997 = 65242
1564584448.964842239 - 1564584448.964726928 = 115311
1564584448.965072859 - 1564584448.964857411 = 215448
1564584448.965513618 - 1564584448.965089549 = 424069
1564584448.966417894 - 1564584448.965532584 = 885310
1564584448.968286377 - 1564584448.966443687 = 1842690
1564584448.971667549 - 1564584448.968314446 = 3353103
1564584448.978288790 - 1564584448.971694101 = 6594689
1564584448.991803618 - 1564584448.978313066 = 13490552
1564584449.017692308 - 1564584448.991836239 = 25856069
1564584449.069651756 - 1564584449.017713549 = 51938207
1564584449.173110928 - 1564584449.069673756 = 103437172
1564584449.380001204 - 1564584449.173132928 = 206868276
1564584449.793857618 - 1564584449.380041411 = 413816207
1564584450.625367342 - 1564584449.793898584 = 831468758
1564584452.299529411 - 1564584450.625426514 = 1674102897
1564584455.665938307 - 1564584452.299592376 = 3366345931
1564584462.331777479 - 1564584455.665973962 = 6665803517
Benchmarking 33554432 samples...
18.107882743 - 12.075641371 = 6032241372
getpid native: 179 ns
34.720410331 - 18.107978605 = 16612431726
getpid RET_ALLOW: 495 ns
Estimated seccomp overhead per syscall: 316 n

--
________________________________________
Carlos Eduardo de Paula
me@xxxxxxxxxxxxx
http://carlosedp.com
http://twitter.com/carlosedp
Linkedin
________________________________________

Next message: Logan Gunthorpe: "Re: [PATCH] iommu/vt-d: Fix wrong analysis whether devices share the same bus"
Previous message: Carlos Eduardo de Paula: "Re: [PATCH v2] riscv: add support for SECCOMP and SECCOMP_FILTER"
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