From: Yiyang Chen <chenyy23@mails.tsinghua.edu.cn>
Date: Thu, 18 Jun 2026 10:18:43 +0000 (+0000)
Subject: bpf: Guard conntrack opts error writes
X-Git-Tag: v7.2-rc1~25^2~2^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6f6183a39533d727deaa5061cadae6dd9e6744d0;p=thirdparty%2Fkernel%2Flinux.git

bpf: Guard conntrack opts error writes

The conntrack lookup and allocation kfuncs take an opts pointer
together with an opts__sz argument. The verifier checks only the memory
range described by opts__sz, but the wrappers unconditionally write
opts->error whenever the internal lookup or allocation helper returns an
error.

For an invalid size smaller than the end of opts->error, that write can
land outside the verifier-checked range. Keep returning NULL for invalid
arguments, but only report the error through opts->error when the
supplied size includes the field.

This preserves error reporting for the supported 12-byte and 16-byte
layouts, and for other invalid sizes that still include opts->error.

Fixes: b4c2b9593a1c ("net/netfilter: Add unstable CT lookup helpers for XDP and TC-BPF")
Fixes: d7e79c97c00c ("net: netfilter: Add kfuncs to allocate and insert CT")
Signed-off-by: Yiyang Chen <chenyy23@mails.tsinghua.edu.cn>
Link: https://lore.kernel.org/r/9535e781fe14449b1d4e9bbc3baa7566a93bf512.1781765747.git.chenyy23@mails.tsinghua.edu.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---

diff --git a/net/netfilter/nf_conntrack_bpf.c b/net/netfilter/nf_conntrack_bpf.c
index 40c261cd0af38..f98d1d4b42c3d 100644
--- a/net/netfilter/nf_conntrack_bpf.c
+++ b/net/netfilter/nf_conntrack_bpf.c
@@ -65,6 +65,15 @@ enum {
 	NF_BPF_CT_OPTS_SZ = 16,
 };
 
+static void *bpf_ct_opts_result(struct bpf_ct_opts *opts, u32 opts__sz, void *ret)
+{
+	if (!IS_ERR(ret))
+		return ret;
+	if (opts__sz >= offsetofend(struct bpf_ct_opts, error))
+		opts->error = PTR_ERR(ret);
+	return NULL;
+}
+
 static int bpf_nf_ct_tuple_parse(struct bpf_sock_tuple *bpf_tuple,
 				 u32 tuple_len, u8 protonum, u8 dir,
 				 struct nf_conntrack_tuple *tuple)
@@ -297,12 +306,7 @@ bpf_xdp_ct_alloc(struct xdp_md *xdp_ctx, struct bpf_sock_tuple *bpf_tuple,
 
 	nfct = __bpf_nf_ct_alloc_entry(dev_net(ctx->rxq->dev), bpf_tuple, tuple__sz,
 				       opts, opts__sz, 10);
-	if (IS_ERR(nfct)) {
-		opts->error = PTR_ERR(nfct);
-		return NULL;
-	}
-
-	return (struct nf_conn___init *)nfct;
+	return (struct nf_conn___init *)bpf_ct_opts_result(opts, opts__sz, nfct);
 }
 
 /* bpf_xdp_ct_lookup - Lookup CT entry for the given tuple, and acquire a
@@ -331,11 +335,7 @@ bpf_xdp_ct_lookup(struct xdp_md *xdp_ctx, struct bpf_sock_tuple *bpf_tuple,
 
 	caller_net = dev_net(ctx->rxq->dev);
 	nfct = __bpf_nf_ct_lookup(caller_net, bpf_tuple, tuple__sz, opts, opts__sz);
-	if (IS_ERR(nfct)) {
-		opts->error = PTR_ERR(nfct);
-		return NULL;
-	}
-	return nfct;
+	return bpf_ct_opts_result(opts, opts__sz, nfct);
 }
 
 /* bpf_skb_ct_alloc - Allocate a new CT entry
@@ -363,12 +363,7 @@ bpf_skb_ct_alloc(struct __sk_buff *skb_ctx, struct bpf_sock_tuple *bpf_tuple,
 
 	net = skb->dev ? dev_net(skb->dev) : sock_net(skb->sk);
 	nfct = __bpf_nf_ct_alloc_entry(net, bpf_tuple, tuple__sz, opts, opts__sz, 10);
-	if (IS_ERR(nfct)) {
-		opts->error = PTR_ERR(nfct);
-		return NULL;
-	}
-
-	return (struct nf_conn___init *)nfct;
+	return (struct nf_conn___init *)bpf_ct_opts_result(opts, opts__sz, nfct);
 }
 
 /* bpf_skb_ct_lookup - Lookup CT entry for the given tuple, and acquire a
@@ -397,11 +392,7 @@ bpf_skb_ct_lookup(struct __sk_buff *skb_ctx, struct bpf_sock_tuple *bpf_tuple,
 
 	caller_net = skb->dev ? dev_net(skb->dev) : sock_net(skb->sk);
 	nfct = __bpf_nf_ct_lookup(caller_net, bpf_tuple, tuple__sz, opts, opts__sz);
-	if (IS_ERR(nfct)) {
-		opts->error = PTR_ERR(nfct);
-		return NULL;
-	}
-	return nfct;
+	return bpf_ct_opts_result(opts, opts__sz, nfct);
 }
 
 /* bpf_ct_insert_entry - Add the provided entry into a CT map