[PATCH 6/9] netfilter: nf_tables: remove WARN and add NLA_STRING upper limits

[Pablo Neira Ayuso <pablo@netfilter.org>]

From: Florian Westphal <fw@strlen.de>

This WARN can trigger because some of the names fed to the module
autoload function can be of arbitrary length.

Remove the WARN and add limits for all NLA_STRING attributes.

Reported-by: syzbot+0e63ae76d117ae1c3a01@syzkaller.appspotmail.com
Fixes: 452238e8d5ffd8 ("netfilter: nf_tables: add and use helper for module autoload")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_tables_api.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 168765d1d1c2..b3692458d428 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -22,6 +22,8 @@
 #include <net/net_namespace.h>
 #include <net/sock.h>
 
+#define NFT_MODULE_AUTOLOAD_LIMIT (MODULE_NAME_LEN - sizeof("nft-expr-255-"))
+
 static LIST_HEAD(nf_tables_expressions);
 static LIST_HEAD(nf_tables_objects);
 static LIST_HEAD(nf_tables_flowtables);
@@ -583,7 +585,7 @@ static void nft_request_module(struct net *net, const char *fmt, ...)
 	va_start(args, fmt);
 	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
 	va_end(args);
-	if (WARN(ret >= MODULE_NAME_LEN, "truncated: '%s' (len %d)", module_name, ret))
+	if (ret >= MODULE_NAME_LEN)
 		return;
 
 	mutex_unlock(&net->nft.commit_mutex);
@@ -1242,7 +1244,8 @@ static const struct nla_policy nft_chain_policy[NFTA_CHAIN_MAX + 1] = {
 				    .len = NFT_CHAIN_MAXNAMELEN - 1 },
 	[NFTA_CHAIN_HOOK]	= { .type = NLA_NESTED },
 	[NFTA_CHAIN_POLICY]	= { .type = NLA_U32 },
-	[NFTA_CHAIN_TYPE]	= { .type = NLA_STRING },
+	[NFTA_CHAIN_TYPE]	= { .type = NLA_STRING,
+				    .len = NFT_MODULE_AUTOLOAD_LIMIT },
 	[NFTA_CHAIN_COUNTERS]	= { .type = NLA_NESTED },
 	[NFTA_CHAIN_FLAGS]	= { .type = NLA_U32 },
 };
@@ -2356,7 +2359,8 @@ static const struct nft_expr_type *nft_expr_type_get(struct net *net,
 }
 
 static const struct nla_policy nft_expr_policy[NFTA_EXPR_MAX + 1] = {
-	[NFTA_EXPR_NAME]	= { .type = NLA_STRING },
+	[NFTA_EXPR_NAME]	= { .type = NLA_STRING,
+				    .len = NFT_MODULE_AUTOLOAD_LIMIT },
 	[NFTA_EXPR_DATA]	= { .type = NLA_NESTED },
 };
 
@@ -4199,7 +4203,8 @@ static const struct nla_policy nft_set_elem_policy[NFTA_SET_ELEM_MAX + 1] = {
 	[NFTA_SET_ELEM_USERDATA]	= { .type = NLA_BINARY,
 					    .len = NFT_USERDATA_MAXLEN },
 	[NFTA_SET_ELEM_EXPR]		= { .type = NLA_NESTED },
-	[NFTA_SET_ELEM_OBJREF]		= { .type = NLA_STRING },
+	[NFTA_SET_ELEM_OBJREF]		= { .type = NLA_STRING,
+					    .len = NFT_OBJ_MAXNAMELEN - 1 },
 };
 
 static const struct nla_policy nft_set_elem_list_policy[NFTA_SET_ELEM_LIST_MAX + 1] = {
-- 
2.11.0