linux-kernel - [PATCH 4.4 37/38] netfilter: xt_RATEEST: reject non-null terminated string from userspace

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Date:   Mon, 11 Jan 2021 14:01:09 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+e86f7c428c8c50db65b4@...kaller.appspotmail.com,
        Florian Westphal <fw@...len.de>,
        Pablo Neira Ayuso <pablo@...filter.org>
Subject: [PATCH 4.4 37/38] netfilter: xt_RATEEST: reject non-null terminated string from userspace

From: Florian Westphal <fw@...len.de>

commit 6cb56218ad9e580e519dcd23bfb3db08d8692e5a upstream.

syzbot reports:
detected buffer overflow in strlen
[..]
Call Trace:
 strlen include/linux/string.h:325 [inline]
 strlcpy include/linux/string.h:348 [inline]
 xt_rateest_tg_checkentry+0x2a5/0x6b0 net/netfilter/xt_RATEEST.c:143

strlcpy assumes src is a c-string. Check info->name before its used.

Reported-by: syzbot+e86f7c428c8c50db65b4@...kaller.appspotmail.com
Fixes: 5859034d7eb8793 ("[NETFILTER]: x_tables: add RATEEST target")
Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/netfilter/xt_RATEEST.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/netfilter/xt_RATEEST.c
+++ b/net/netfilter/xt_RATEEST.c
@@ -107,6 +107,9 @@ static int xt_rateest_tg_checkentry(cons
 	} cfg;
 	int ret;
 
+	if (strnlen(info->name, sizeof(est->name)) >= sizeof(est->name))
+		return -ENAMETOOLONG;
+
 	if (unlikely(!rnd_inited)) {
 		get_random_bytes(&jhash_rnd, sizeof(jhash_rnd));
 		rnd_inited = true;