diff mbox series

[v2,nf-next,6/7] netfilter: nf_tables: must hold rcu read lock while iterating expression type list

Message ID 20241030094053.13118-7-fw@strlen.de
State Changes Requested
Headers show
Series netfilter: nf_tables: avoid PROVE_RCU_LIST splats | expand

Commit Message

Florian Westphal Oct. 30, 2024, 9:40 a.m. UTC 
nft shell tests trigger:
 WARNING: suspicious RCU usage
 net/netfilter/nf_tables_api.c:3125 RCU-list traversed in non-reader section!!
 1 lock held by nft/2068:
  #0: ffff888106c6f8c8 (&nft_net->commit_mutex){+.+.}-{4:4}, at: nf_tables_valid_genid+0x3c/0xf0

But the transaction mutex doesn't protect this list, the nfnl subsystem
mutex would, but we can't acquire it here without risk of ABBA
deadlocks.

Acquire the rcu read lock and also reject any types that reside in
modules, we'd need to extend this to hold a module reference.

Fixes: 3a07327d10a0 ("netfilter: nft_inner: support for inner tunnel header matching")
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 v2: reject owner != NULL, not == NULL.

 net/netfilter/nf_tables_api.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)
diff mbox series

Patch

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 3b5154f2dd79..c588cab98260 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3296,25 +3296,37 @@  int nft_expr_inner_parse(const struct nft_ctx *ctx, const struct nlattr *nla,
 	if (!tb[NFTA_EXPR_DATA] || !tb[NFTA_EXPR_NAME])
 		return -EINVAL;
 
+	rcu_read_lock();
+
 	type = __nft_expr_type_get(ctx->family, tb[NFTA_EXPR_NAME]);
-	if (!type)
-		return -ENOENT;
+	if (!type) {
+		err = -ENOENT;
+		goto out_unlock;
+	}
 
-	if (!type->inner_ops)
-		return -EOPNOTSUPP;
+	if (!type->inner_ops || type->owner) {
+		err = -EOPNOTSUPP;
+		goto out_unlock;
+	}
 
 	err = nla_parse_nested_deprecated(info->tb, type->maxattr,
 					  tb[NFTA_EXPR_DATA],
 					  type->policy, NULL);
 	if (err < 0)
-		goto err_nla_parse;
+		goto out_unlock;
 
 	info->attr = nla;
 	info->ops = type->inner_ops;
 
+	/* At this time only meta and payload are supported, both are
+	 * builtin.  Therefore we can get away without a module
+	 * reference.
+	 */
+	rcu_read_unlock();
 	return 0;
 
-err_nla_parse:
+out_unlock:
+	rcu_read_unlock();
 	return err;
 }