Commit 5340627e authored by David Abdurachmanov's avatar David Abdurachmanov Committed by Paul Walmsley
Browse files

riscv: add support for SECCOMP and SECCOMP_FILTER 

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 immediately if secure_computing(NULL) returns -1
  - fixed whitespace issues
  - add missing seccomp.h
  - remove patch #2 (solved now)
  - add riscv to seccomp kernel selftest

Signed-off-by: default avatarDavid Abdurachmanov <david.abdurachmanov@sifive.com>
Cc: keescook@chromium.org
Cc: me@carlosedp.com
Tested-by: default avatarCarlos de Paula <me@carlosedp.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/linux-riscv/CAEn-LTp=ss0Dfv6J00=rCAy+N78U2AmhqJNjfqjr2FDpPYjxEQ@mail.gmail.com/
Link: https://lore.kernel.org/linux-riscv/CAJr-aD=UnCN9E_mdVJ2H5nt=6juRSWikZnA5HxDLQxXLbsRz-w@mail.gmail.com/


[paul.walmsley@sifive.com: cleaned up Cc: lines; fixed spelling and
 checkpatch issues; updated to apply]
Signed-off-by: default avatarPaul Walmsley <paul.walmsley@sifive.com>
parent 00a5bf3a

arch/riscv/Kconfig

+14 −0
Original line number Diff line number Diff line
@@ -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_ASM_MODVERSIONS

	select HAVE_MEMBLOCK_NODE_MAP

	select HAVE_DMA_CONTIGUOUS
@@ -272,6 +273,19 @@ 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"

arch/riscv/include/asm/seccomp.h

0 → 100644
+10 −0
Original line number Diff line number Diff line 
/* 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 */

arch/riscv/include/asm/thread_info.h

+4 −1
Original line number Diff line number Diff line
@@ -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 */

arch/riscv/kernel/entry.S

+25 −2
Original line number Diff line number Diff line
@@ -226,8 +226,25 @@ 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
@@ -238,6 +255,12 @@ 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

arch/riscv/kernel/ptrace.c

+10 −0
Original line number Diff line number Diff line
@@ -154,6 +154,16 @@ __visible 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));

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