linux-kernel - [PATCH bpf-next] bpf: Replace offsetof() with struct

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Message-ID: <20250428210638.30219-2-thorsten.blum@linux.dev>
Date: Mon, 28 Apr 2025 23:06:39 +0200
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	John Fastabend <john.fastabend@...il.com>,
	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>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>
Cc: Thorsten Blum <thorsten.blum@...ux.dev>,
	bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next] bpf: Replace offsetof() with struct_size()

Compared to offsetof(), struct_size() provides additional compile-time
checks for structs with flexible arrays (e.g., __must_be_array()).

No functional changes intended.

Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
---
 kernel/bpf/syscall.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 9794446bc8c6..d7287f3e260b 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -36,6 +36,7 @@
 #include <linux/memcontrol.h>
 #include <linux/trace_events.h>
 #include <linux/tracepoint.h>
+#include <linux/overflow.h>
 
 #include <net/netfilter/nf_bpf_link.h>
 #include <net/netkit.h>
@@ -693,7 +694,7 @@ struct btf_record *btf_record_dup(const struct btf_record *rec)
 
 	if (IS_ERR_OR_NULL(rec))
 		return NULL;
-	size = offsetof(struct btf_record, fields[rec->cnt]);
+	size = struct_size(rec, fields, rec->cnt);
 	new_rec = kmemdup(rec, size, GFP_KERNEL | __GFP_NOWARN);
 	if (!new_rec)
 		return ERR_PTR(-ENOMEM);
@@ -748,7 +749,7 @@ bool btf_record_equal(const struct btf_record *rec_a, const struct btf_record *r
 		return false;
 	if (rec_a->cnt != rec_b->cnt)
 		return false;
-	size = offsetof(struct btf_record, fields[rec_a->cnt]);
+	size = struct_size(rec_a, fields, rec_a->cnt);
 	/* btf_parse_fields uses kzalloc to allocate a btf_record, so unused
 	 * members are zeroed out. So memcmp is safe to do without worrying
 	 * about padding/unused fields.
-- 
2.49.0