From 42309ab450b608ddcfafa90e4cfa93a5001ecfba Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Fri, 27 Jun 2014 17:01:47 +0100 Subject: [PATCH] ARM: 8087/1: ptrace: reload syscall number after secure_computing() check On the syscall tracing path, we call out to secure_computing() to allow seccomp to check the syscall number being attempted. As part of this, a SIGTRAP may be sent to the tracer and the syscall could be re-written by a subsequent SET_SYSCALL ptrace request. Unfortunately, this new syscall is ignored by the current code unless TIF_SYSCALL_TRACE is also set on the current thread. This patch slightly reworks the enter path of the syscall tracing code so that we always reload the syscall number from current_thread_info()->syscall after the potential ptrace traps. Acked-by: Kees Cook Tested-by: Kees Cook Signed-off-by: Will Deacon Signed-off-by: Russell King --- arch/arm/kernel/ptrace.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c index 0dd3b79..0c27ed6 100644 --- a/arch/arm/kernel/ptrace.c +++ b/arch/arm/kernel/ptrace.c @@ -908,7 +908,7 @@ enum ptrace_syscall_dir { PTRACE_SYSCALL_EXIT, }; -static int tracehook_report_syscall(struct pt_regs *regs, +static void tracehook_report_syscall(struct pt_regs *regs, enum ptrace_syscall_dir dir) { unsigned long ip; @@ -926,7 +926,6 @@ static int tracehook_report_syscall(struct pt_regs *regs, current_thread_info()->syscall = -1; regs->ARM_ip = ip; - return current_thread_info()->syscall; } asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno) @@ -938,7 +937,9 @@ asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno) return -1; if (test_thread_flag(TIF_SYSCALL_TRACE)) - scno = tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER); + tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER); + + scno = current_thread_info()->syscall; if (test_thread_flag(TIF_SYSCALL_TRACEPOINT)) trace_sys_enter(regs, scno); -- 2.7.4