x86/ptrace: run seccomp after ptrace
This moves seccomp after ptrace on x86 to that seccomp can catch changes
made by ptrace. Emulation should skip the rest of processing too.
We can get rid of test_thread_flag because there's no longer any
opportunity for seccomp to mess with ptrace state before invoking
ptrace.
Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: x86@kernel.org
Cc: Andy Lutomirski <luto@kernel.org>
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index df56ca3..81c0e12 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -73,6 +73,7 @@
struct thread_info *ti = pt_regs_to_thread_info(regs);
unsigned long ret = 0;
+ bool emulated = false;
u32 work;
if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
@@ -80,11 +81,19 @@
work = ACCESS_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;
+ if (unlikely(work & _TIF_SYSCALL_EMU))
+ emulated = true;
+
+ if ((emulated || (work & _TIF_SYSCALL_TRACE)) &&
+ tracehook_report_syscall_entry(regs))
+ return -1L;
+
+ if (emulated)
+ return -1L;
+
#ifdef CONFIG_SECCOMP
/*
- * Do seccomp first -- it should minimize exposure of other
- * code, and keeping seccomp fast is probably more valuable
- * than the rest of this.
+ * Do seccomp after ptrace, to catch any tracer changes.
*/
if (work & _TIF_SECCOMP) {
struct seccomp_data sd;
@@ -117,13 +126,6 @@
}
#endif
- if (unlikely(work & _TIF_SYSCALL_EMU))
- ret = -1L;
-
- if ((ret || test_thread_flag(TIF_SYSCALL_TRACE)) &&
- tracehook_report_syscall_entry(regs))
- ret = -1L;
-
if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
trace_sys_enter(regs, regs->orig_ax);