netdev - [PATCH net-next 17/19] netfilter: xt_nfacct: don't assume acct name is null-terminated

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Message-Id: <20250725170340.21327-18-pablo@netfilter.org>
Date: Fri, 25 Jul 2025 19:03:38 +0200
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net,
	netdev@...r.kernel.org,
	kuba@...nel.org,
	pabeni@...hat.com,
	edumazet@...gle.com,
	fw@...len.de,
	horms@...nel.org
Subject: [PATCH net-next 17/19] netfilter: xt_nfacct: don't assume acct name is null-terminated

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

BUG: KASAN: slab-out-of-bounds in .. lib/vsprintf.c:721
Read of size 1 at addr ffff88801eac95c8 by task syz-executor183/5851
[..]
 string+0x231/0x2b0 lib/vsprintf.c:721
 vsnprintf+0x739/0xf00 lib/vsprintf.c:2874
 [..]
 nfacct_mt_checkentry+0xd2/0xe0 net/netfilter/xt_nfacct.c:41
 xt_check_match+0x3d1/0xab0 net/netfilter/x_tables.c:523

nfnl_acct_find_get() handles non-null input, but the error
printk relied on its presence.

Reported-by: syzbot+4ff165b9251e4d295690@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=4ff165b9251e4d295690
Tested-by: syzbot+4ff165b9251e4d295690@...kaller.appspotmail.com
Fixes: ceb98d03eac5 ("netfilter: xtables: add nfacct match to support extended accounting")
Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/xt_nfacct.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/xt_nfacct.c b/net/netfilter/xt_nfacct.c
index 7c6bf1c16813..0ca1cdfc4095 100644
--- a/net/netfilter/xt_nfacct.c
+++ b/net/netfilter/xt_nfacct.c
@@ -38,8 +38,8 @@ nfacct_mt_checkentry(const struct xt_mtchk_param *par)
 
 	nfacct = nfnl_acct_find_get(par->net, info->name);
 	if (nfacct == NULL) {
-		pr_info_ratelimited("accounting object `%s' does not exists\n",
-				    info->name);
+		pr_info_ratelimited("accounting object `%.*s' does not exist\n",
+				    NFACCT_NAME_MAX, info->name);
 		return -ENOENT;
 	}
 	info->nfacct = nfacct;
-- 
2.30.2