Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965106AbbFJPrd (ORCPT ); Wed, 10 Jun 2015 11:47:33 -0400 Received: from ip4-83-240-67-251.cust.nbox.cz ([83.240.67.251]:36155 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933852AbbFJP1v (ORCPT ); Wed, 10 Jun 2015 11:27:51 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Alexei Starovoitov , "David S. Miller" , Jiri Slaby Subject: [PATCH 3.12 089/111] x86: bpf_jit: fix compilation of large bpf programs Date: Wed, 10 Jun 2015 17:27:18 +0200 Message-Id: <0fa9520e7b08f00138cf9a4a95d066492cbcc18d.1433943052.git.jslaby@suse.cz> X-Mailer: git-send-email 2.4.2 In-Reply-To: <93091169a673f49c2574cddf1ef858cf0704f646.1433943052.git.jslaby@suse.cz> References: <93091169a673f49c2574cddf1ef858cf0704f646.1433943052.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2263 Lines: 55 From: Alexei Starovoitov 3.12-stable review patch. If anyone has any objections, please let me know. =============== [ 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: Jiri Slaby --- arch/x86/net/bpf_jit_comp.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 4ed75dd81d05..1b72000b6be2 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -211,7 +211,12 @@ void bpf_jit_compile(struct sk_filter *fp) } cleanup_addr = proglen; /* epilogue address */ - 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++) { u8 seen_or_pass0 = (pass == 0) ? (SEEN_XREG | SEEN_DATAREF | SEEN_MEM) : seen; /* no prologue/epilogue for trivial filters (RET something) */ proglen = 0; -- 2.4.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/