arm64/ptrace: Return early for ptrace_report_syscall_entry() error

The generic entry abort the syscall_trace_enter() sequence if
ptrace_report_syscall_entry() errors out, but arm64 not.

When ptrace requests interception, it should prevent all subsequent
system-call processing, including audit and seccomp. In preparation for
moving arm64 over to the generic entry code, return early if
ptrace_report_syscall_entry() encounters an error.

Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Signed-off-by: Will Deacon <will@kernel.org>

Author: ruanjinjie-eng

arch/arm64/kernel/ptrace.c

@@ -2372,15 +2372,18 @@ static __always_inline unsigned long ptrace_save_reg(struct pt_regs *regs,
 	return saved_reg;
 }
 
-static void report_syscall_entry(struct pt_regs *regs)
+static int report_syscall_entry(struct pt_regs *regs)
 {
 	unsigned long saved_reg;
-	int regno;
+	int regno, ret;
 
 	saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_ENTER, &regno);
-	if (ptrace_report_syscall_entry(regs))
+	ret = ptrace_report_syscall_entry(regs);
+	if (ret)
 		forget_syscall(regs);
 	regs->regs[regno] = saved_reg;
+
+	return ret;
 }
 
 static void report_syscall_exit(struct pt_regs *regs)
@@ -2407,10 +2410,11 @@ static void report_syscall_exit(struct pt_regs *regs)
 int syscall_trace_enter(struct pt_regs *regs)
 {
 	unsigned long flags = read_thread_flags();
+	int ret;
 
 	if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
-		report_syscall_entry(regs);
-		if (flags & _TIF_SYSCALL_EMU)
+		ret = report_syscall_entry(regs);
+		if (ret || (flags & _TIF_SYSCALL_EMU))
 			return NO_SYSCALL;
 	}