On Sat, Jun 27, 2026 at 10:16:43PM +0100, David Laight wrote: > On Fri, 26 Jun 2026 17:25:35 -0500 > Ian Bridges <[email protected]> wrote: > > > 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 <[email protected]> > > --- > > 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); > > If you are going to use snprintf either paste the strings together: > snprintf(buf, sizeof(buf), "%s" FORMAT_TABLES, xt_prefix[af]); > or prepend the "%s" onto the #define of FORMAT_TABLES itself: > snprintf(buf, sizeof(buf), FORMAT_TABLES, xt_prefix[af]); >
I learned something new today, thanks. I'll use the first form in v2. > FORMAT_TABLES should also be FORMAT_NAMES. The macro is already named FORMAT_TABLES today, so that rename would be a cleanup of pre-existing code rather than part of the strlcat conversion. I'm happy to fold it into v2 if a maintainer is fine including the tidy-up in this patch. Thanks for the review, Ian > > -- David > > > 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*/ > > } >
