move seccomp from /proc to a prctl
This reduces the memory footprint and it enforces that only the current
task can enable seccomp on itself (this is a requirement for a
strightforward [modulo preempt ;) ] TIF_NOTSC implementation).
Signed-off-by: Andrea Arcangeli <andrea@cpushare.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index c3391b60..1dfa8a5 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -10,6 +10,7 @@
#include <linux/sched.h>
/* #define SECCOMP_DEBUG 1 */
+#define NR_SECCOMP_MODES 1
/*
* Secure computing mode 1 allows only read/write/exit/sigreturn.
@@ -54,3 +55,28 @@
#endif
do_exit(SIGKILL);
}
+
+long prctl_get_seccomp(void)
+{
+ return current->seccomp.mode;
+}
+
+long prctl_set_seccomp(unsigned long seccomp_mode)
+{
+ long ret;
+
+ /* can set it only once to be even more secure */
+ ret = -EPERM;
+ if (unlikely(current->seccomp.mode))
+ goto out;
+
+ ret = -EINVAL;
+ if (seccomp_mode && seccomp_mode <= NR_SECCOMP_MODES) {
+ current->seccomp.mode = seccomp_mode;
+ set_thread_flag(TIF_SECCOMP);
+ ret = 0;
+ }
+
+ out:
+ return ret;
+}
diff --git a/kernel/sys.c b/kernel/sys.c
index ed92e2f..4d141ae 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -31,6 +31,7 @@
#include <linux/cn_proc.h>
#include <linux/getcpu.h>
#include <linux/task_io_accounting_ops.h>
+#include <linux/seccomp.h>
#include <linux/compat.h>
#include <linux/syscalls.h>
@@ -2242,6 +2243,13 @@
error = SET_ENDIAN(current, arg2);
break;
+ case PR_GET_SECCOMP:
+ error = prctl_get_seccomp();
+ break;
+ case PR_SET_SECCOMP:
+ error = prctl_set_seccomp(arg2);
+ break;
+
default:
error = -EINVAL;
break;