* [PATCH] netfilter: x_tables: replace strlcat() with snprintf() @ 2026-06-26 22:25 Ian Bridges 2026-06-27 21:16 ` David Laight 0 siblings, 1 reply; 4+ messages in thread From: Ian Bridges @ 2026-06-26 22:25 UTC (permalink / raw) To: Pablo Neira Ayuso, Florian Westphal, Phil Sutter, David S. Miller, Eric Dumazet, Jakub Kicinski, Paolo Abeni, Simon Horman, netfilter-devel, coreteam, netdev, linux-kernel Cc: linux-hardening 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 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] netfilter: x_tables: replace strlcat() with snprintf() 2026-06-26 22:25 [PATCH] netfilter: x_tables: replace strlcat() with snprintf() Ian Bridges @ 2026-06-27 21:16 ` David Laight 2026-07-01 6:25 ` Ian Bridges 0 siblings, 1 reply; 4+ messages in thread From: David Laight @ 2026-06-27 21:16 UTC (permalink / raw) To: Ian Bridges Cc: Pablo Neira Ayuso, Florian Westphal, Phil Sutter, David S. Miller, Eric Dumazet, Jakub Kicinski, Paolo Abeni, Simon Horman, netfilter-devel, coreteam, netdev, linux-kernel, linux-hardening On Fri, 26 Jun 2026 17:25:35 -0500 Ian Bridges <icb@fastmail.org> 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 <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); 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]); FORMAT_TABLES should also be FORMAT_NAMES. -- 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*/ > } ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] netfilter: x_tables: replace strlcat() with snprintf() 2026-06-27 21:16 ` David Laight @ 2026-07-01 6:25 ` Ian Bridges 2026-07-01 6:31 ` Florian Westphal 0 siblings, 1 reply; 4+ messages in thread From: Ian Bridges @ 2026-07-01 6:25 UTC (permalink / raw) To: David Laight Cc: Pablo Neira Ayuso, Florian Westphal, Phil Sutter, David S. Miller, Eric Dumazet, Jakub Kicinski, Paolo Abeni, Simon Horman, netfilter-devel, coreteam, netdev, linux-kernel, linux-hardening On Sat, Jun 27, 2026 at 10:16:43PM +0100, David Laight wrote: > On Fri, 26 Jun 2026 17:25:35 -0500 > Ian Bridges <icb@fastmail.org> 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 <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); > > 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*/ > > } > ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] netfilter: x_tables: replace strlcat() with snprintf() 2026-07-01 6:25 ` Ian Bridges @ 2026-07-01 6:31 ` Florian Westphal 0 siblings, 0 replies; 4+ messages in thread From: Florian Westphal @ 2026-07-01 6:31 UTC (permalink / raw) To: Ian Bridges Cc: David Laight, Pablo Neira Ayuso, Phil Sutter, David S. Miller, Eric Dumazet, Jakub Kicinski, Paolo Abeni, Simon Horman, netfilter-devel, coreteam, netdev, linux-kernel, linux-hardening Ian Bridges <icb@fastmail.org> wrote: > I learned something new today, thanks. I'll use the first form in v2. > > > FORMAT_TABLES should also be FORMAT_NAMES. No. The name is fine. > 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. No need for a v2, I mangled this patch locally already to use "%s_FOO" in FORMAT_FOO. ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2026-07-01 6:31 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2026-06-26 22:25 [PATCH] netfilter: x_tables: replace strlcat() with snprintf() Ian Bridges 2026-06-27 21:16 ` David Laight 2026-07-01 6:25 ` Ian Bridges 2026-07-01 6:31 ` Florian Westphal
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox