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netfilter: nf_tables: Don't allocate nft_rule_dump_ctx

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Since struct netlink_callback::args is not used by rule dumpers anymore,
use it to hold nft_rule_dump_ctx. Add a build-time check to make sure it
won't ever exceed the available space.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>
This commit is contained in:
Phil Sutter 2023-09-29 21:19:22 +02:00 committed by Florian Westphal
parent 8194d599bc
commit 99ab9f84b8
1 changed files with 6 additions and 13 deletions
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19
net/netfilter/nf_tables_api.c
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@ -3453,7 +3453,7 @@ static int __nf_tables_dump_rules(struct sk_buff *skb,
const struct nft_table *table,
const struct nft_chain *chain)
{
struct nft_rule_dump_ctx *ctx = cb->data;
struct nft_rule_dump_ctx *ctx = (void *)cb->ctx;
struct net *net = sock_net(skb->sk);
const struct nft_rule *rule, *prule;
unsigned int entries = 0;
@ -3498,7 +3498,7 @@ static int nf_tables_dump_rules(struct sk_buff *skb,
struct netlink_callback *cb)
{
const struct nfgenmsg *nfmsg = nlmsg_data(cb->nlh);
struct nft_rule_dump_ctx *ctx = cb->data;
struct nft_rule_dump_ctx *ctx = (void *)cb->ctx;
struct nft_table *table;
const struct nft_chain *chain;
unsigned int idx = 0;
@ -3553,42 +3553,35 @@ static int nf_tables_dump_rules(struct sk_buff *skb,
static int nf_tables_dump_rules_start(struct netlink_callback *cb)
{
struct nft_rule_dump_ctx *ctx = (void *)cb->ctx;
const struct nlattr * const *nla = cb->data;
struct nft_rule_dump_ctx *ctx = NULL;
ctx = kzalloc(sizeof(*ctx), GFP_ATOMIC);
if (!ctx)
return -ENOMEM;
BUILD_BUG_ON(sizeof(*ctx) > sizeof(cb->ctx));
if (nla[NFTA_RULE_TABLE]) {
ctx->table = nla_strdup(nla[NFTA_RULE_TABLE], GFP_ATOMIC);
if (!ctx->table) {
kfree(ctx);
if (!ctx->table)
return -ENOMEM;
}
}
if (nla[NFTA_RULE_CHAIN]) {
ctx->chain = nla_strdup(nla[NFTA_RULE_CHAIN], GFP_ATOMIC);
if (!ctx->chain) {
kfree(ctx->table);
kfree(ctx);
return -ENOMEM;
}
}
if (NFNL_MSG_TYPE(cb->nlh->nlmsg_type) == NFT_MSG_GETRULE_RESET)
ctx->reset = true;
cb->data = ctx;
return 0;
}
static int nf_tables_dump_rules_done(struct netlink_callback *cb)
{
struct nft_rule_dump_ctx *ctx = cb->data;
struct nft_rule_dump_ctx *ctx = (void *)cb->ctx;
kfree(ctx->table);
kfree(ctx->chain);
kfree(ctx);
return 0;
}