[PATCH] netfilter: x_tables: replace strlcat() with snprintf()

[PATCH] netfilter: x_tables: replace strlcat() with snprintf()

[Ian Bridges]

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