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bpf: Guard conntrack opts error writes

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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: b4c2b9593a ("net/netfilter: Add unstable CT lookup helpers for XDP and TC-BPF")
Fixes: d7e79c97c0 ("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>
This commit is contained in:
Yiyang Chen 2026-06-18 10:18:43 +00:00 committed by Alexei Starovoitov
parent 8816d94303
commit 6f6183a395
1 changed files with 13 additions and 22 deletions
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35
net/netfilter/nf_conntrack_bpf.c
View File

@ -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