From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH] bpf: fix divides by zero Date: Fri, 12 Jan 2018 17:33:26 -0800 Message-ID: <1515807206.3606.4.camel@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Cc: netdev , edumazet@google.com To: Alexei Starovoitov , Daniel Borkmann Return-path: Received: from mail-pf0-f193.google.com ([209.85.192.193]:34560 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965242AbeAMBda (ORCPT ); Fri, 12 Jan 2018 20:33:30 -0500 Received: by mail-pf0-f193.google.com with SMTP id e76so5668732pfk.1 for ; Fri, 12 Jan 2018 17:33:29 -0800 (PST) Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet 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 ---  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 51ec2dda7f08c6c90af084589bb6d80662c77d12..7949e8b8f94e9cc196e0449214493 ccce61b0903 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -956,7 +956,7 @@ 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); @@ -975,7 +975,7 @@ 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);