Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752114AbbFYMsL (ORCPT ); Thu, 25 Jun 2015 08:48:11 -0400 Received: from mail-pd0-f182.google.com ([209.85.192.182]:33151 "EHLO mail-pd0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751568AbbFYMrz (ORCPT ); Thu, 25 Jun 2015 08:47:55 -0400 From: Xi Wang To: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, Xi Wang , Zi Shen Lim , Alexei Starovoitov , Will Deacon Subject: [PATCH] arm64: bpf: fix out-of-bounds read in bpf2a64_offset() Date: Thu, 25 Jun 2015 05:47:39 -0700 Message-Id: <1435236459-15141-1-git-send-email-xi.wang@gmail.com> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1899 Lines: 55 Problems occur when bpf_to or bpf_from has value prog->len - 1 (e.g., "Very long jump backwards" in test_bpf where the last instruction is a jump): since ctx->offset has length prog->len, ctx->offset[bpf_to + 1] or ctx->offset[bpf_from + 1] will cause an out-of-bounds read, leading to a bogus jump offset and kernel panic. This patch moves updating ctx->offset to after calling build_insn(), and changes indexing to use bpf_to and bpf_from without + 1. Cc: Zi Shen Lim Cc: Alexei Starovoitov Cc: Will Deacon Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler") Signed-off-by: Xi Wang --- arch/arm64/net/bpf_jit_comp.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index dc6a484..c81ddd4 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -113,9 +113,9 @@ static inline void emit_a64_mov_i(const int is64, const int reg, static inline int bpf2a64_offset(int bpf_to, int bpf_from, const struct jit_ctx *ctx) { - int to = ctx->offset[bpf_to + 1]; + int to = ctx->offset[bpf_to]; /* -1 to account for the Branch instruction */ - int from = ctx->offset[bpf_from + 1] - 1; + int from = ctx->offset[bpf_from] - 1; return to - from; } @@ -640,10 +640,11 @@ static int build_body(struct jit_ctx *ctx) const struct bpf_insn *insn = &prog->insnsi[i]; int ret; + ret = build_insn(insn, ctx); + if (ctx->image == NULL) ctx->offset[i] = ctx->idx; - ret = build_insn(insn, ctx); if (ret > 0) { i++; continue; -- 2.1.4 -- 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/