1 files changed, 30 insertions, 13 deletions

diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index 739db3a1b2d2..03deeffd9f6d 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -916,16 +916,11 @@ enum ptrace_syscall_dir {
 	PTRACE_SYSCALL_EXIT,
 };
 
-static int ptrace_syscall_trace(struct pt_regs *regs, int scno,
-				enum ptrace_syscall_dir dir)
+static int tracehook_report_syscall(struct pt_regs *regs,
+				    enum ptrace_syscall_dir dir)
 {
 	unsigned long ip;
 
-	current_thread_info()->syscall = scno;
-
-	if (!test_thread_flag(TIF_SYSCALL_TRACE))
-		return scno;
-
 	/*
 	 * IP is used to denote syscall entry/exit:
 	 * IP = 0 -> entry, =1 -> exit
@@ -944,19 +939,41 @@ static int ptrace_syscall_trace(struct pt_regs *regs, int scno,
 
 asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno)
 {
-	scno = ptrace_syscall_trace(regs, scno, PTRACE_SYSCALL_ENTER);
+	current_thread_info()->syscall = scno;
+
+	/* Do the secure computing check first; failures should be fast. */
+	if (secure_computing(scno) == -1)
+		return -1;
+
+	if (test_thread_flag(TIF_SYSCALL_TRACE))
+		scno = tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
+
 	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
 		trace_sys_enter(regs, scno);
+
 	audit_syscall_entry(AUDIT_ARCH_ARM, scno, regs->ARM_r0, regs->ARM_r1,
 			    regs->ARM_r2, regs->ARM_r3);
+
 	return scno;
 }
 
-asmlinkage int syscall_trace_exit(struct pt_regs *regs, int scno)
+asmlinkage void syscall_trace_exit(struct pt_regs *regs)
 {
-	scno = ptrace_syscall_trace(regs, scno, PTRACE_SYSCALL_EXIT);
-	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
-		trace_sys_exit(regs, scno);
+	/*
+	 * Audit the syscall before anything else, as a debugger may
+	 * come in and change the current registers.
+	 */
 	audit_syscall_exit(regs);
-	return scno;
+
+	/*
+	 * Note that we haven't updated the ->syscall field for the
+	 * current thread. This isn't a problem because it will have
+	 * been set on syscall entry and there hasn't been an opportunity
+	 * for a PTRACE_SET_SYSCALL since then.
+	 */
+	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
+		trace_sys_exit(regs, regs_return_value(regs));
+
+	if (test_thread_flag(TIF_SYSCALL_TRACE))
+		tracehook_report_syscall(regs, PTRACE_SYSCALL_EXIT);
 }