Commit cddc0427 authored Nov 04, 2024 by Florian Westphal Committed by Pablo Neira Ayuso Nov 05, 2024

netfilter: nf_tables: must hold rcu read lock while iterating object type list



Update of stateful object triggers:
WARNING: suspicious RCU usage
net/netfilter/nf_tables_api.c:7759 RCU-list traversed in non-reader section!!

other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
1 lock held by nft/3060:
 #0: ffff88810f0578c8 (&nft_net->commit_mutex){+.+.}-{4:4}, [..]

... but this list is not protected by the transaction mutex but the
nfnl nftables subsystem mutex.

Switch to nft_obj_type_get which will acquire rcu read lock,
bump refcount, and returns the result.

v3: Dan Carpenter points out nft_obj_type_get returns error pointer, not
NULL, on error.

Fixes: dad3bdee ("netfilter: nf_tables: fix memory leak during stateful obj update").
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

parent ee666a54

net/netfilter/nf_tables_api.c

+6 −7

Original line number	Diff line number	Diff line
		@@ -7809,9 +7809,7 @@ static int nf_tables_updobj(const struct nft_ctx *ctx,
		struct nft_trans *trans;
		int err = -ENOMEM;

		if (!try_module_get(type->owner))
		return -ENOENT;

		/* caller must have obtained type->owner reference. */
		trans = nft_trans_alloc(ctx, NFT_MSG_NEWOBJ,
		sizeof(struct nft_trans_obj));
		if (!trans)
		@@ -7879,15 +7877,16 @@ static int nf_tables_newobj(struct sk_buff skb, const struct nfnl_info info,
		if (info->nlh->nlmsg_flags & NLM_F_REPLACE)
		return -EOPNOTSUPP;

		type = __nft_obj_type_get(objtype, family);
		if (WARN_ON_ONCE(!type))
		return -ENOENT;

		if (!obj->ops->update)
		return 0;

		type = nft_obj_type_get(net, objtype, family);
		if (WARN_ON_ONCE(IS_ERR(type)))
		return PTR_ERR(type);

		nft_ctx_init(&ctx, net, skb, info->nlh, family, table, NULL, nla);

		/* type->owner reference is put when transaction object is released. */
		return nf_tables_updobj(&ctx, type, nla[NFTA_OBJ_DATA], obj);
		}