libbpf: Guard add_data() against size overflow

add_data() computes size8 = roundup(size, 8) and then hands size8 to
realloc_data_buf() before doing memcpy(gen->data_cur, data, size) with
the original size. A wrapped size8 passes through the realloc_data_buf()
INT32_MAX check. Harden this against overflow, though not realistic to
happen in practice.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260602133052.423725-3-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: borkmann

tools/lib/bpf/gen_loader.c

@@ -160,10 +160,16 @@ void bpf_gen__init(struct bpf_gen *gen, int log_level, int nr_progs, int nr_maps
 
 static int add_data(struct bpf_gen *gen, const void *data, __u32 size)
 {
-	__u32 size8 = roundup(size, 8);
 	__u64 zero = 0;
+	__u32 size8;
 	void *prev;
 
+	if (size > INT32_MAX) {
+		gen->error = -ERANGE;
+		return 0;
+	}
+	size8 = roundup(size, 8);
+
 	if (realloc_data_buf(gen, size8))
 		return 0;
 	prev = gen->data_cur;