linux-kernel - [PATCH 09/14] MIPS/ptrace: run seccomp after ptrace

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Date:	Thu,  9 Jun 2016 14:01:59 -0700
From:	Kees Cook <keescook@...omium.org>
To:	linux-kernel@...r.kernel.org
Cc:	Kees Cook <keescook@...omium.org>,
	Ralf Baechle <ralf@...ux-mips.org>,
	"Maciej W. Rozycki" <macro@...tec.com>,
	James Hogan <james.hogan@...tec.com>,
	linux-mips@...ux-mips.org, Andy Lutomirski <luto@...nel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Chris Metcalf <cmetcalf@...lanox.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Helge Deller <deller@....de>,
	"James E.J. Bottomley" <jejb@...isc-linux.org>,
	Jeff Dike <jdike@...toit.com>, linux-arch@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-parisc@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	Mark Rutland <mark.rutland@....com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Paul Mackerras <paulus@...ba.org>,
	Richard Weinberger <richard@....at>,
	Russell King <linux@...linux.org.uk>,
	user-mode-linux-devel@...ts.sourceforge.net,
	Will Deacon <will.deacon@....com>, x86@...nel.org
Subject: [PATCH 09/14] MIPS/ptrace: run seccomp after ptrace

Close the hole where ptrace can change a syscall out from under seccomp.

Signed-off-by: Kees Cook <keescook@...omium.org>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: "Maciej W. Rozycki" <macro@...tec.com>
Cc: James Hogan <james.hogan@...tec.com>
Cc: linux-mips@...ux-mips.org
---
 arch/mips/kernel/ptrace.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c
index c50af846ecf9..6103b24d1bfc 100644
--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -888,17 +888,16 @@ long arch_ptrace(struct task_struct *child, long request,
  */
 asmlinkage long syscall_trace_enter(struct pt_regs *regs, long syscall)
 {
-	long ret = 0;
 	user_exit();
 
 	current_thread_info()->syscall = syscall;
 
-	if (secure_computing(NULL) == -1)
-		return -1;
-
 	if (test_thread_flag(TIF_SYSCALL_TRACE) &&
 	    tracehook_report_syscall_entry(regs))
-		ret = -1;
+		return -1;
+
+	if (secure_computing(NULL) == -1)
+		return -1;
 
 	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
 		trace_sys_enter(regs, regs->regs[2]);
-- 
2.7.4