bpf: Account scratch buffer in bpf_prog_calc_tag

bpf_prog_calc_tag() copies the instructions into a plain vmalloc() scratch
buffer to blind the map fds before hashing. The buffer scales with the
program, up to ~8MB at the 1M instruction limit, and is allocated on every
program load, but unlike the rest of the load-time scratch memory it is
not charged to the loader's memcg. Use GFP_KERNEL_ACCOUNT to account it
like the other allocations scoped to the verification/load.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20260708211537.371874-5-daniel@iogearbox.net
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

kernel/bpf/core.c

@@ -305,7 +305,7 @@ int bpf_prog_calc_tag(struct bpf_prog *fp)
 	bool was_ld_map;
 	u32 i;
 
-	dst = vmalloc(size);
+	dst = __vmalloc(size, GFP_KERNEL_ACCOUNT);
 	if (!dst)
 		return -ENOMEM;