From: Ian Bridges <icb@fastmail.org>
To: Pablo Neira Ayuso <pablo@netfilter.org>,
Florian Westphal <fw@strlen.de>, Phil Sutter <phil@nwl.cc>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Simon Horman <horms@kernel.org>,
netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: linux-hardening@vger.kernel.org
Subject: [PATCH] netfilter: x_tables: replace strlcat() with snprintf()
Date: Fri, 26 Jun 2026 17:25:35 -0500 [thread overview]
Message-ID: <aj78X4Cjqcpbb8Co@dev> (raw)
In preparation for removing the deprecated strlcat() API[1], replace the
strscpy()/strlcat() pairs in xt_proto_init() and xt_proto_fini() with
snprintf(), which builds each /proc file name in a single call.
Each name is "<prefix><suffix>", where <prefix> is the address-family
string xt_prefix[af] and <suffix> is one of the FORMAT_TABLES,
FORMAT_MATCHES or FORMAT_TARGETS literals. snprintf() with a "%s%s"
format produces the same NUL-terminated, length-bounded string as the
strscpy()/strlcat() chain it replaces, so the proc entry names are
unchanged.
Link: https://github.com/KSPP/linux/issues/370 [1]
Signed-off-by: Ian Bridges <icb@fastmail.org>
---
net/netfilter/x_tables.c | 24 ++++++++----------------
1 file changed, 8 insertions(+), 16 deletions(-)
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 4e6708c23922..56f4546be336 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -2033,8 +2033,7 @@ int xt_proto_init(struct net *net, u_int8_t af)
root_uid = make_kuid(net->user_ns, 0);
root_gid = make_kgid(net->user_ns, 0);
- strscpy(buf, xt_prefix[af], sizeof(buf));
- strlcat(buf, FORMAT_TABLES, sizeof(buf));
+ snprintf(buf, sizeof(buf), "%s%s", xt_prefix[af], FORMAT_TABLES);
proc = proc_create_net_data(buf, 0440, net->proc_net, &xt_table_seq_ops,
sizeof(struct seq_net_private),
(void *)(unsigned long)af);
@@ -2043,8 +2042,7 @@ int xt_proto_init(struct net *net, u_int8_t af)
if (uid_valid(root_uid) && gid_valid(root_gid))
proc_set_user(proc, root_uid, root_gid);
- strscpy(buf, xt_prefix[af], sizeof(buf));
- strlcat(buf, FORMAT_MATCHES, sizeof(buf));
+ snprintf(buf, sizeof(buf), "%s%s", xt_prefix[af], FORMAT_MATCHES);
proc = proc_create_seq_private(buf, 0440, net->proc_net,
&xt_match_seq_ops, sizeof(struct nf_mttg_trav),
(void *)(unsigned long)af);
@@ -2053,8 +2051,7 @@ int xt_proto_init(struct net *net, u_int8_t af)
if (uid_valid(root_uid) && gid_valid(root_gid))
proc_set_user(proc, root_uid, root_gid);
- strscpy(buf, xt_prefix[af], sizeof(buf));
- strlcat(buf, FORMAT_TARGETS, sizeof(buf));
+ snprintf(buf, sizeof(buf), "%s%s", xt_prefix[af], FORMAT_TARGETS);
proc = proc_create_seq_private(buf, 0440, net->proc_net,
&xt_target_seq_ops, sizeof(struct nf_mttg_trav),
(void *)(unsigned long)af);
@@ -2068,13 +2065,11 @@ int xt_proto_init(struct net *net, u_int8_t af)
#ifdef CONFIG_PROC_FS
out_remove_matches:
- strscpy(buf, xt_prefix[af], sizeof(buf));
- strlcat(buf, FORMAT_MATCHES, sizeof(buf));
+ snprintf(buf, sizeof(buf), "%s%s", xt_prefix[af], FORMAT_MATCHES);
remove_proc_entry(buf, net->proc_net);
out_remove_tables:
- strscpy(buf, xt_prefix[af], sizeof(buf));
- strlcat(buf, FORMAT_TABLES, sizeof(buf));
+ snprintf(buf, sizeof(buf), "%s%s", xt_prefix[af], FORMAT_TABLES);
remove_proc_entry(buf, net->proc_net);
out:
return -1;
@@ -2087,16 +2082,13 @@ void xt_proto_fini(struct net *net, u_int8_t af)
#ifdef CONFIG_PROC_FS
char buf[XT_FUNCTION_MAXNAMELEN];
- strscpy(buf, xt_prefix[af], sizeof(buf));
- strlcat(buf, FORMAT_TABLES, sizeof(buf));
+ snprintf(buf, sizeof(buf), "%s%s", xt_prefix[af], FORMAT_TABLES);
remove_proc_entry(buf, net->proc_net);
- strscpy(buf, xt_prefix[af], sizeof(buf));
- strlcat(buf, FORMAT_TARGETS, sizeof(buf));
+ snprintf(buf, sizeof(buf), "%s%s", xt_prefix[af], FORMAT_TARGETS);
remove_proc_entry(buf, net->proc_net);
- strscpy(buf, xt_prefix[af], sizeof(buf));
- strlcat(buf, FORMAT_MATCHES, sizeof(buf));
+ snprintf(buf, sizeof(buf), "%s%s", xt_prefix[af], FORMAT_MATCHES);
remove_proc_entry(buf, net->proc_net);
#endif /*CONFIG_PROC_FS*/
}
--
2.47.3
reply other threads:[~2026-06-26 22:25 UTC|newest]
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