From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martynas Pumputis Subject: [PATCH v2] bpf: fix check of allowed specifiers in bpf_trace_printk Date: Fri, 23 Nov 2018 17:43:26 +0100 Message-ID: <20181123164326.28127-1-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]:47787 "EHLO out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729195AbeKXDbL (ORCPT ); Fri, 23 Nov 2018 22:31:11 -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 | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 08fcfe440c63..9864a35c8bb5 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -196,11 +196,13 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1, i++; } else if (fmt[i] == 'p' || fmt[i] == 's') { mod[fmt_cnt]++; - i++; - if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0) + /* disallow any further format extensions */ + if (fmt[i + 1] != 0 && + !isspace(fmt[i + 1]) && + !ispunct(fmt[i + 1])) return -EINVAL; fmt_cnt++; - if (fmt[i - 1] == 's') { + if (fmt[i] == 's') { if (str_seen) /* allow only one '%s' per fmt string */ return -EINVAL; -- 2.19.1