Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946142AbbFSVTW (ORCPT ); Fri, 19 Jun 2015 17:19:22 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:51440 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756062AbbFSUjH (ORCPT ); Fri, 19 Jun 2015 16:39:07 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Borkmann , Alexei Starovoitov , "David S. Miller" Subject: [PATCH 4.0 005/105] x86: bpf_jit: fix compilation of large bpf programs Date: Fri, 19 Jun 2015 13:34:55 -0700 Message-Id: <20150619203558.368229595@linuxfoundation.org> X-Mailer: git-send-email 2.4.4 In-Reply-To: <20150619203558.187802739@linuxfoundation.org> References: <20150619203558.187802739@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1965 Lines: 50 4.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alexei Starovoitov [ Upstream commit 3f7352bf21f8fd7ba3e2fcef9488756f188e12be ] x86 has variable length encoding. x86 JIT compiler is trying to pick the shortest encoding for given bpf instruction. While doing so the jump targets are changing, so JIT is doing multiple passes over the program. Typical program needs 3 passes. Some very short programs converge with 2 passes. Large programs may need 4 or 5. But specially crafted bpf programs may hit the pass limit and if the program converges on the last iteration the JIT compiler will be producing an image full of 'int 3' insns. Fix this corner case by doing final iteration over bpf program. Fixes: 0a14842f5a3c ("net: filter: Just In Time compiler for x86-64") Reported-by: Daniel Borkmann Signed-off-by: Alexei Starovoitov Tested-by: Daniel Borkmann Acked-by: Daniel Borkmann Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- arch/x86/net/bpf_jit_comp.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -966,7 +966,12 @@ void bpf_int_jit_compile(struct bpf_prog } ctx.cleanup_addr = proglen; - for (pass = 0; pass < 10; pass++) { + /* JITed image shrinks with every pass and the loop iterates + * until the image stops shrinking. Very large bpf programs + * may converge on the last pass. In such case do one more + * pass to emit the final image + */ + for (pass = 0; pass < 10 || image; pass++) { proglen = do_jit(prog, addrs, image, oldproglen, &ctx); if (proglen <= 0) { image = NULL; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in Please read the FAQ at http://www.tux.org/lkml/