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-rw-r--r--arch/um/Kconfig.common1
-rw-r--r--arch/um/Kconfig.um16
-rw-r--r--arch/um/include/asm/thread_info.h2
-rw-r--r--arch/um/kernel/skas/syscall.c5
4 files changed, 24 insertions, 0 deletions
diff --git a/arch/um/Kconfig.common b/arch/um/Kconfig.common
index d195a87ca542..cc0013475444 100644
--- a/arch/um/Kconfig.common
+++ b/arch/um/Kconfig.common
@@ -2,6 +2,7 @@ config UML
bool
default y
select HAVE_ARCH_AUDITSYSCALL
+ select HAVE_ARCH_SECCOMP_FILTER
select HAVE_UID16
select HAVE_FUTEX_CMPXCHG if FUTEX
select GENERIC_IRQ_SHOW
diff --git a/arch/um/Kconfig.um b/arch/um/Kconfig.um
index 28a9885e3a37..4b2ed5858b2e 100644
--- a/arch/um/Kconfig.um
+++ b/arch/um/Kconfig.um
@@ -104,3 +104,19 @@ config PGTABLE_LEVELS
int
default 3 if 3_LEVEL_PGTABLES
default 2
+
+config SECCOMP
+ def_bool y
+ 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.
+
+ If unsure, say Y.
diff --git a/arch/um/include/asm/thread_info.h b/arch/um/include/asm/thread_info.h
index 53968aaf76f9..053baff03674 100644
--- a/arch/um/include/asm/thread_info.h
+++ b/arch/um/include/asm/thread_info.h
@@ -62,11 +62,13 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_SYSCALL_AUDIT 6
#define TIF_RESTORE_SIGMASK 7
#define TIF_NOTIFY_RESUME 8
+#define TIF_SECCOMP 9 /* secure computing */
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_MEMDIE (1 << TIF_MEMDIE)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
+#define _TIF_SECCOMP (1 << TIF_SECCOMP)
#endif
diff --git a/arch/um/kernel/skas/syscall.c b/arch/um/kernel/skas/syscall.c
index 6cadce761bcf..48b0dcbd87be 100644
--- a/arch/um/kernel/skas/syscall.c
+++ b/arch/um/kernel/skas/syscall.c
@@ -5,6 +5,7 @@
#include <linux/kernel.h>
#include <linux/ptrace.h>
+#include <linux/seccomp.h>
#include <kern_util.h>
#include <sysdep/ptrace.h>
#include <sysdep/ptrace_user.h>
@@ -19,6 +20,10 @@ void handle_syscall(struct uml_pt_regs *r)
UPT_SYSCALL_NR(r) = PT_SYSCALL_NR(r->gp);
PT_REGS_SET_SYSCALL_RETURN(regs, -ENOSYS);
+ /* Do the secure computing check first; failures should be fast. */
+ if (secure_computing() == -1)
+ return;
+
if (syscall_trace_enter(regs))
goto out;