netdev - [PATCH bpf-next v3 14/17] bpf, verifier: Track when data

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Message-Id: <20260107-skb-meta-safeproof-netdevs-rx-only-v3-14-0d461c5e4764@cloudflare.com>
Date: Wed, 07 Jan 2026 15:28:14 +0100
From: Jakub Sitnicki <jakub@...udflare.com>
To: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 Jesper Dangaard Brouer <hawk@...nel.org>, 
 John Fastabend <john.fastabend@...il.com>, 
 Stanislav Fomichev <sdf@...ichev.me>, Simon Horman <horms@...nel.org>, 
 Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
 Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
 kernel-team@...udflare.com
Subject: [PATCH bpf-next v3 14/17] bpf, verifier: Track when data_meta
 pointer is loaded

Introduce PA_F_DATA_META_LOAD flag to track when a BPF program loads the
skb->data_meta pointer.

This information will be used by gen_prologue() to handle cases where there
is a gap between metadata end and skb->data, requiring metadata to be
realigned.

Reviewed-by: Eduard Zingerman <eddyz87@...il.com>
Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
---
 include/linux/bpf_verifier.h | 1 +
 kernel/bpf/verifier.c        | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index c8397ae51880..b32ddf0f0ab3 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -649,6 +649,7 @@ enum priv_stack_mode {

 enum packet_access_flags {
 	PA_F_DIRECT_WRITE = BIT(0),
+	PA_F_DATA_META_LOAD = BIT(1),
 };

 struct bpf_subprog_info {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index daa90c81d802..76f2befc8159 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6226,6 +6226,10 @@ static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off,
 		} else {
 			env->insn_aux_data[insn_idx].ctx_field_size = info->ctx_field_size;
 		}
+
+		if (base_type(info->reg_type) == PTR_TO_PACKET_META)
+			env->seen_packet_access |= PA_F_DATA_META_LOAD;
+
 		/* remember the offset of last byte accessed in ctx */
 		if (env->prog->aux->max_ctx_offset < off + size)
 			env->prog->aux->max_ctx_offset = off + size;

-- 
2.43.0