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