From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A2498322B69 for ; Thu, 5 Feb 2026 06:38:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770273492; cv=none; b=c9JSrrBeB/jODgmNwHtACvEPbkU2A/pR9Bh2U7jJq4UMLNQWT+stAI9BnIQiaXeWgpdMT02sENaVimtEKqS5HBjBvGlK1pfBxnTZPcLIrdblEl//he9C9M0ZVS2hvIiJ7QsVz3O3TdO8KkxZyyR/bXnH3f7/mXQrnUhMXJ5pBF8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770273492; c=relaxed/simple; bh=0yd3vl9ueFi69vzy5bKtA8iHjYXoRZY6bH5RzkXrKnI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=QYcxOytD17II95oqVMfTVwudS+nP7mhroMrI2u14nbG6weJkS5Z+A3V6XpvGZzlZwBf+uLLkDCg3hHXOA/hdBdyowZCo1bq3/I8r2cSLwXyOG7g8zBQzT10po1foqe21bdTlW6OA4GZj2agCT7rDCK40+1rU5XRZVPDPLcgpcsw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AXKKlYTo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AXKKlYTo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 209D8C4CEF7; Thu, 5 Feb 2026 06:38:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770273492; bh=0yd3vl9ueFi69vzy5bKtA8iHjYXoRZY6bH5RzkXrKnI=; h=From:To:Cc:Subject:Date:From; b=AXKKlYToam59wC03EQsDxhv8HsTSRbdy6J7PwSXiZmS9u0MUgfIkjhhIq+psc2hge D605mqhR68tie413OUCXnBlGHwDcfbw+LFqcsCo7VCVgvdRp+vzFD6ZgaqiWWtc2J7 8L7iT3kEFLUhBj2+S8PG9xe/6+kbPHBcnssr1PqQIQkOng5mEiwa9njaQARwFeCP0r N3n80k149gjDeu5jtS5zOwpCE1qETwvJ5bsKd5KAdXFyw3QkfxOkocGtyAJhNKXAuA 1hshK04UwZRhprNzX997Ym0R9RLwa/CJb0FdCZHslh442v/n580FdpJtZfCzgV0zB5 rFPbcAI85DrMg== From: KP Singh To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, clm@meta.com, KP Singh Subject: [PATCH bpf v3] bpf: Limit signature size to KMALLOC_MAX_CACHE_SIZE Date: Thu, 5 Feb 2026 07:38:07 +0100 Message-ID: <20260205063807.690823-1-kpsingh@kernel.org> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- kernel/bpf/syscall.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 4ff82144f885..15e87f507991 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2820,6 +2820,12 @@ 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 -- 2.43.0