From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from www62.your-server.de ([213.133.104.62]:54199 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752978AbeA1XhB (ORCPT ); Sun, 28 Jan 2018 18:37:01 -0500 From: Daniel Borkmann To: gregkh@linuxfoundation.org Cc: ast@kernel.org, stable@vger.kernel.org, Eric Dumazet Subject: [PATCH stable 4.14 3/6] bpf: fix divides by zero Date: Mon, 29 Jan 2018 00:36:44 +0100 Message-Id: <20180128233647.21154-4-daniel@iogearbox.net> In-Reply-To: <20180128233647.21154-1-daniel@iogearbox.net> References: <20180128233647.21154-1-daniel@iogearbox.net> Sender: stable-owner@vger.kernel.org List-ID: From: Eric Dumazet [ upstream commit c366287ebd698ef5e3de300d90cd62ee9ee7373e ] Divides by zero are not nice, lets avoid them if possible. Also do_div() seems not needed when dealing with 32bit operands, but this seems a minor detail. Fixes: bd4cf0ed331a ("net: filter: rework/optimize internal BPF interpreter's instruction set") Signed-off-by: Eric Dumazet Reported-by: syzbot Signed-off-by: Alexei Starovoitov --- kernel/bpf/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index aaa4424..2246115 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -949,7 +949,7 @@ static unsigned int ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, DST = tmp; CONT; ALU_MOD_X: - if (unlikely(SRC == 0)) + if (unlikely((u32)SRC == 0)) return 0; tmp = (u32) DST; DST = do_div(tmp, (u32) SRC); @@ -968,7 +968,7 @@ static unsigned int ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, DST = div64_u64(DST, SRC); CONT; ALU_DIV_X: - if (unlikely(SRC == 0)) + if (unlikely((u32)SRC == 0)) return 0; tmp = (u32) DST; do_div(tmp, (u32) SRC); -- 2.9.5