From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martynas Pumputis Subject: [PATCH] bpf: fix check of allowed specifiers in bpf_trace_printk Date: Thu, 22 Nov 2018 17:00:30 +0100 Message-ID: <20181122160030.15954-1-m@lambda.lt> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: ast@kernel.org, daniel@iogearbox.net, m@lambda.lt To: netdev@vger.kernel.org Return-path: Received: from out4-smtp.messagingengine.com ([66.111.4.28]:43205 "EHLO out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391924AbeKWClQ (ORCPT ); Thu, 22 Nov 2018 21:41:16 -0500 Sender: netdev-owner@vger.kernel.org List-ID: A format string consisting of "%p" or "%s" followed by an invalid specifier (e.g. "%p%\n" or "%s%") could pass the check which would make format_decode (lib/vsprintf.c) to warn. Reported-by: syzbot+1ec5c5ec949c4adaa0c4@syzkaller.appspotmail.com Signed-off-by: Martynas Pumputis --- kernel/trace/bpf_trace.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 08fcfe440c63..9ab05736e1a1 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -225,6 +225,8 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1, (void *) (long) unsafe_addr, sizeof(buf)); } + if (fmt[i] == '%') + i--; continue; } -- 2.19.1