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 <l...@kernel.org>
Signed-off-by: Kees Cook <keesc...@chromium.org>
Cc: x...@kernel.org
Cc: Andy Lutomirski <l...@kernel.org>
---
arch/x86/entry/common.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index df56ca394877..81c0e12d831c 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -73,6 +73,7 @@ static long syscall_trace_enter(struct pt_regs *regs)
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 @@ static long syscall_trace_enter(struct pt_regs *regs)
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 @@ static long syscall_trace_enter(struct pt_regs *regs)
}
#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);
--
2.7.4
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