seccomp,x86,arm,mips,s390: Remove nr parameter from secure_computing

The secure_computing function took a syscall number parameter, but
it only paid any attention to that parameter if seccomp mode 1 was
enabled.  Rather than coming up with a kludge to get the parameter
to work in mode 2, just remove the parameter.

To avoid churn in arches that don't have seccomp filters (and may
not even support syscall_get_nr right now), this leaves the
parameter in secure_computing_strict, which is now a real function.

For ARM, this is a bit ugly due to the fact that ARM conditionally
supports seccomp filters.  Fixing that would probably only be a
couple of lines of code, but it should be coordinated with the audit
maintainers.

This will be a slight slowdown on some arches.  The right fix is to
pass in all of seccomp_data instead of trying to make just the
syscall nr part be fast.

This is a prerequisite for making two-phase seccomp work cleanly.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux-s390@vger.kernel.org
Cc: x86@kernel.org
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Kees Cook <keescook@chromium.org>

7 files changed, 66 insertions, 34 deletions

diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index 0c27ed6f3f23..5e772a21ab97 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -933,8 +933,13 @@ asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno)
         current_thread_info()->syscall = scno;
 
         /* Do the secure computing check first; failures should be fast. */
-        if (secure_computing(scno) == -1)
+#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
+        if (secure_computing() == -1)
                 return -1;
+#else
+        /* XXX: remove this once OABI gets fixed */
+        secure_computing_strict(scno);
+#endif
 
         if (test_thread_flag(TIF_SYSCALL_TRACE))
                 tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c
index 645b3c4fcfba..f7aac5b57b4b 100644
--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -770,7 +770,7 @@ asmlinkage long syscall_trace_enter(struct pt_regs *regs, long syscall)
         long ret = 0;
         user_exit();
 
-        if (secure_computing(syscall) == -1)
+        if (secure_computing() == -1)
                 return -1;
 
         if (test_thread_flag(TIF_SYSCALL_TRACE) &&
diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index 5dc7ad9e2fbf..bebacad48305 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -803,7 +803,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
         long ret = 0;
 
         /* Do the secure computing check first. */
-        if (secure_computing(regs->gprs[2])) {
+        if (secure_computing()) {
                 /* seccomp failures shouldn't expose any additional code. */
                 ret = -1;
                 goto out;
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 678c0ada3b3c..93c182a00506 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -1471,7 +1471,7 @@ long syscall_trace_enter(struct pt_regs *regs)
                 regs->flags |= X86_EFLAGS_TF;
 
         /* do the secure computing check first */
-        if (secure_computing(regs->orig_ax)) {
+        if (secure_computing()) {
                 /* seccomp failures shouldn't expose any additional code. */
                 ret = -1L;
                 goto out;
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index e1e1e80fc6a6..957779f4eb40 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -216,7 +216,7 @@ bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
          */
         regs->orig_ax = syscall_nr;
         regs->ax = -ENOSYS;
-        tmp = secure_computing(syscall_nr);
+        tmp = secure_computing();
         if ((!tmp && regs->orig_ax != syscall_nr) || regs->ip != address) {
                 warn_bad_vsyscall(KERN_DEBUG, regs,
                                   "seccomp tried to change syscall nr or ip");
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index 5d586a45a319..aa3c040230be 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -27,19 +27,17 @@ struct seccomp {
         struct seccomp_filter *filter;
 };
 
-extern int __secure_computing(int);
-static inline int secure_computing(int this_syscall)
+#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
+extern int __secure_computing(void);
+static inline int secure_computing(void)
 {
         if (unlikely(test_thread_flag(TIF_SECCOMP)))
-                return  __secure_computing(this_syscall);
+                return  __secure_computing();
         return 0;
 }
-
-/* A wrapper for architectures supporting only SECCOMP_MODE_STRICT. */
-static inline void secure_computing_strict(int this_syscall)
-{
-        BUG_ON(secure_computing(this_syscall) != 0);
-}
+#else
+extern void secure_computing_strict(int this_syscall);
+#endif
 
 extern long prctl_get_seccomp(void);
 extern long prctl_set_seccomp(unsigned long, char __user *);
@@ -56,8 +54,11 @@ static inline int seccomp_mode(struct seccomp *s)
 struct seccomp { };
 struct seccomp_filter { };
 
-static inline int secure_computing(int this_syscall) { return 0; }
+#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
+static inline int secure_computing(void) { return 0; }
+#else
 static inline void secure_computing_strict(int this_syscall) { return; }
+#endif
 
 static inline long prctl_get_seccomp(void)
 {
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 44eb005c6695..5e738e0dd2e9 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -23,8 +23,11 @@
 
 /* #define SECCOMP_DEBUG 1 */
 
-#ifdef CONFIG_SECCOMP_FILTER
+#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
 #include <asm/syscall.h>
+#endif
+
+#ifdef CONFIG_SECCOMP_FILTER
 #include <linux/filter.h>
 #include <linux/pid.h>
 #include <linux/ptrace.h>
@@ -172,7 +175,7 @@ static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
  *
  * Returns valid seccomp BPF response codes.
  */
-static u32 seccomp_run_filters(int syscall)
+static u32 seccomp_run_filters(void)
 {
         struct seccomp_filter *f = ACCESS_ONCE(current->seccomp.filter);
         struct seccomp_data sd;
@@ -564,10 +567,43 @@ static int mode1_syscalls_32[] = {
 };
 #endif
 
-int __secure_computing(int this_syscall)
+static void __secure_computing_strict(int this_syscall)
+{
+        int *syscall_whitelist = mode1_syscalls;
+#ifdef CONFIG_COMPAT
+        if (is_compat_task())
+                syscall_whitelist = mode1_syscalls_32;
+#endif
+        do {
+                if (*syscall_whitelist == this_syscall)
+                        return;
+        } while (*++syscall_whitelist);
+
+#ifdef SECCOMP_DEBUG
+        dump_stack();
+#endif
+        audit_seccomp(this_syscall, SIGKILL, SECCOMP_RET_KILL);
+        do_exit(SIGKILL);
+}
+
+#ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER
+void secure_computing_strict(int this_syscall)
+{
+        int mode = current->seccomp.mode;
+
+        if (mode == 0)
+                return;
+        else if (mode == SECCOMP_MODE_STRICT)
+                __secure_computing_strict(this_syscall);
+        else
+                BUG();
+}
+#else
+int __secure_computing(void)
 {
+        struct pt_regs *regs = task_pt_regs(current);
+        int this_syscall = syscall_get_nr(current, regs);
         int exit_sig = 0;
-        int *syscall;
         u32 ret;
 
         /*
@@ -578,23 +614,12 @@ int __secure_computing(int this_syscall)
 
         switch (current->seccomp.mode) {
         case SECCOMP_MODE_STRICT:
-                syscall = mode1_syscalls;
-#ifdef CONFIG_COMPAT
-                if (is_compat_task())
-                        syscall = mode1_syscalls_32;
-#endif
-                do {
-                        if (*syscall == this_syscall)
-                                return 0;
-                } while (*++syscall);
-                exit_sig = SIGKILL;
-                ret = SECCOMP_RET_KILL;
-                break;
+                __secure_computing_strict(this_syscall);
+                return 0;
 #ifdef CONFIG_SECCOMP_FILTER
         case SECCOMP_MODE_FILTER: {
                 int data;
-                struct pt_regs *regs = task_pt_regs(current);
-                ret = seccomp_run_filters(this_syscall);
+                ret = seccomp_run_filters();
                 data = ret & SECCOMP_RET_DATA;
                 ret &= SECCOMP_RET_ACTION;
                 switch (ret) {
@@ -652,9 +677,10 @@ int __secure_computing(int this_syscall)
 #ifdef CONFIG_SECCOMP_FILTER
 skip:
         audit_seccomp(this_syscall, exit_sig, ret);
-#endif
         return -1;
+#endif
 }
+#endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */
 
 long prctl_get_seccomp(void)
 {