Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1418665

[PATCH 05/14] seccomp: recheck the syscall after RET_TRACE

Show all headers | View raw

When RET_TRACE triggers, a tracer may change a syscall into something that
should be filtered by seccomp. This re-runs seccomp after a trace event
to make sure things continue to pass.

Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@kernel.org>
---
 kernel/seccomp.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 14a37d71b612..54d15eb2b701 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -556,7 +556,8 @@ void secure_computing_strict(int this_syscall)
 #else
 
 #ifdef CONFIG_SECCOMP_FILTER
-static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd)
+static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
+			    const bool recheck_after_trace)
 {
 	u32 filter_ret, action;
 	int data;
@@ -588,6 +589,10 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd)
 		goto skip;
 
 	case SECCOMP_RET_TRACE:
+		/* We've been put in this state by the ptracer already. */
+		if (recheck_after_trace)
+			return 0;
+
 		/* ENOSYS these calls if there is no tracer attached. */
 		if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
 			syscall_set_return_value(current,
@@ -611,6 +616,15 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd)
 		if (this_syscall < 0)
 			goto skip;
 
+		/*
+		 * Recheck the syscall, since it may have changed. This
+		 * intentionally uses a NULL struct seccomp_data to force
+		 * a reload of all registers. This does not goto skip since
+		 * a skip would have already been reported.
+		 */
+		if (__seccomp_filter(this_syscall, NULL, true))
+			return -1;
+
 		return 0;
 
 	case SECCOMP_RET_ALLOW:
@@ -629,7 +643,8 @@ skip:
 	return -1;
 }
 #else
-static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd)
+static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
+			    const bool recheck_after_trace)
 {
 	BUG();
 }
@@ -652,7 +667,7 @@ int __secure_computing(const struct seccomp_data *sd)
 		__secure_computing_strict(this_syscall);  /* may call do_exit */
 		return 0;
 	case SECCOMP_MODE_FILTER:
-		return __seccomp_filter(this_syscall, sd);
+		return __seccomp_filter(this_syscall, sd, false);
 	default:
 		BUG();
 	}
-- 
2.7.4

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH 00/14] run seccomp after ptrace Kees Cook <keescook@chromium.org> - 2016-06-09 23:10 +0200
  [PATCH 10/14] parisc/ptrace: run seccomp after ptrace Kees Cook <keescook@chromium.org> - 2016-06-09 23:10 +0200
  [PATCH 11/14] s390/ptrace: run seccomp after ptrace Kees Cook <keescook@chromium.org> - 2016-06-09 23:10 +0200
    Re: [PATCH 11/14] s390/ptrace: run seccomp after ptrace Martin Schwidefsky <schwidefsky@de.ibm.com> - 2016-06-10 13:00 +0200
  [PATCH 01/14] seccomp: add tests for ptrace hole Kees Cook <keescook@chromium.org> - 2016-06-09 23:10 +0200
  [PATCH 05/14] seccomp: recheck the syscall after RET_TRACE Kees Cook <keescook@chromium.org> - 2016-06-09 23:10 +0200
    Re: [PATCH 05/14] seccomp: recheck the syscall after RET_TRACE Andy Lutomirski <luto@amacapital.net> - 2016-06-10 00:50 +0200
  [PATCH 06/14] x86/ptrace: run seccomp after ptrace Kees Cook <keescook@chromium.org> - 2016-06-09 23:10 +0200
    Re: [PATCH 06/14] x86/ptrace: run seccomp after ptrace Andy Lutomirski <luto@amacapital.net> - 2016-06-10 01:00 +0200
      Re: [PATCH 06/14] x86/ptrace: run seccomp after ptrace Kees Cook <keescook@chromium.org> - 2016-06-10 04:10 +0200
  [PATCH 07/14] arm/ptrace: run seccomp after ptrace Kees Cook <keescook@chromium.org> - 2016-06-09 23:10 +0200
  [PATCH 03/14] x86/entry: Get rid of two-phase syscall entry work Kees Cook <keescook@chromium.org> - 2016-06-09 23:10 +0200

csiph-web