[PATCH] ARM: SECCOMP support
Nicolas Pitre
nico at fluxnic.net
Thu Sep 23 17:11:36 EDT 2010
Signed-off-by: Nicolas Pitre <nicolas.pitre at linaro.org>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 553b7cf..09b890e 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1438,6 +1438,20 @@ config UACCESS_WITH_MEMCPY
However, if the CPU data cache is using a write-allocate mode,
this option is unlikely to provide any performance gain.
+config SECCOMP
+ bool
+ prompt "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.
+
config CC_STACKPROTECTOR
bool "Enable -fstack-protector buffer overflow detection (EXPERIMENTAL)"
help
diff --git a/arch/arm/include/asm/seccomp.h b/arch/arm/include/asm/seccomp.h
new file mode 100644
index 0000000..52b156b
--- /dev/null
+++ b/arch/arm/include/asm/seccomp.h
@@ -0,0 +1,11 @@
+#ifndef _ASM_ARM_SECCOMP_H
+#define _ASM_ARM_SECCOMP_H
+
+#include <linux/unistd.h>
+
+#define __NR_seccomp_read __NR_read
+#define __NR_seccomp_write __NR_write
+#define __NR_seccomp_exit __NR_exit
+#define __NR_seccomp_sigreturn __NR_rt_sigreturn
+
+#endif /* _ASM_ARM_SECCOMP_H */
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 763e29f..7b5cc8d 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -144,6 +144,7 @@ extern void vfp_flush_hwstate(struct thread_info *);
#define TIF_MEMDIE 18 /* is terminating due to OOM killer */
#define TIF_FREEZE 19
#define TIF_RESTORE_SIGMASK 20
+#define TIF_SECCOMP 21
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
@@ -153,6 +154,7 @@ extern void vfp_flush_hwstate(struct thread_info *);
#define _TIF_USING_IWMMXT (1 << TIF_USING_IWMMXT)
#define _TIF_FREEZE (1 << TIF_FREEZE)
#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
+#define _TIF_SECCOMP (1 << TIF_SECCOMP)
/*
* Change these and you break ASM code in entry-common.S
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index f05a35a..cdd0a88 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -314,6 +314,16 @@ ENTRY(vector_swi)
tst ip, #_TIF_SYSCALL_TRACE @ are we tracing syscalls?
bne __sys_trace
+#ifdef CONFIG_SECCOMP
+ tst ip, #_TIF_SECCOMP
+ beq 1f
+ mov r0, scno
+ bl __secure_computing
+ add r0, sp, #S_R0 + S_OFF @ pointer to regs
+ ldmia r0, {r0 - r3} @ have to reload r0 - r3
+1:
+#endif
+
cmp scno, #NR_syscalls @ check upper syscall limit
adr lr, BSYM(ret_fast_syscall) @ return address
ldrcc pc, [tbl, scno, lsl #2] @ call sys_* routine
@@ -336,8 +346,15 @@ __sys_trace:
mov r0, #0 @ trace entry [IP = 0]
bl syscall_trace
- adr lr, BSYM(__sys_trace_return) @ return address
mov scno, r0 @ syscall number (possibly new)
+
+#ifdef CONFIG_SECCOMP
+ ldr ip, [tsk, #TI_FLAGS] @ check for syscall tracing
+ tst ip, #_TIF_SECCOMP
+ blne __secure_computing
+#endif
+
+ adr lr, BSYM(__sys_trace_return) @ return address
add r1, sp, #S_R0 + S_OFF @ pointer to regs
cmp scno, #NR_syscalls @ check upper syscall limit
ldmccia r1, {r0 - r3} @ have to reload r0 - r3
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