From ea1535e28bb3773fc0b3cbd1f3842b808016990c Mon Sep 17 00:00:00 2001 From: KP Singh Date: Thu, 5 Feb 2026 07:38:07 +0100 Subject: [PATCH] bpf: Limit bpf program signature size Practical BPF signatures are significantly smaller than KMALLOC_MAX_CACHE_SIZE Allowing larger sizes opens the door for abuse by passing excessive size values and forcing the kernel into expensive allocation paths (via kmalloc_large or vmalloc). Fixes: 349271568303 ("bpf: Implement signature verification for BPF programs") Reported-by: Chris Mason Signed-off-by: KP Singh Acked-by: Daniel Borkmann Link: https://lore.kernel.org/r/20260205063807.690823-1-kpsingh@kernel.org Signed-off-by: Alexei Starovoitov --- kernel/bpf/syscall.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 5f59dd47a5b1c..93bc0f4c65c57 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2813,6 +2813,13 @@ static int bpf_prog_verify_signature(struct bpf_prog *prog, union bpf_attr *attr void *sig; int err = 0; + /* + * Don't attempt to use kmalloc_large or vmalloc for signatures. + * Practical signature for BPF program should be below this limit. + */ + if (attr->signature_size > KMALLOC_MAX_CACHE_SIZE) + return -EINVAL; + if (system_keyring_id_check(attr->keyring_id) == 0) key = bpf_lookup_system_key(attr->keyring_id); else -- 2.47.3