From nobody Mon Dec 15 23:52:03 2025 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 5962C30F932; Mon, 15 Dec 2025 15:43:58 +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=1765813439; cv=none; b=OTLrNKSnBTp8UPc+r/XRlWe+IJKpZoY4KeFpGGbbB/ErxOFcIwKq851WoocDIXPqJSoo0/VGkMiHf2wH/zlREUnoqtu1vJHnS2/OJhPfQApCesfa0CE5I0m91ACUuiqqE3lBR5FMSlk/X7BlofU4lY+ZLQctDNgvFPDrNJAK2O8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765813439; c=relaxed/simple; bh=2AxnBcqPgqXCnldBOy07VtuaCRIG8GxLYWiW94+3UqM=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=cwVN5AGXhbYv36/qO9wCw8Xi8Wsz5I2GK6nODq1FJ9gkB4IecTC5rzuh/lyqOCky7SJvAkqUXJ/Np/NrnnMjraGYML8P+f0mL1k8AKqJlki6uTNYFXdInbYfV2VGowPCGA2h0tCaXdjktgdQPAjgEd4t9Wakti1lo1UMojmRj9U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lQlYxjcu; 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="lQlYxjcu" Received: by smtp.kernel.org (Postfix) with ESMTPS id D80B4C116B1; Mon, 15 Dec 2025 15:43:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1765813437; bh=2AxnBcqPgqXCnldBOy07VtuaCRIG8GxLYWiW94+3UqM=; h=From:Date:Subject:To:Cc:From; b=lQlYxjcuBzpRZCNQ3UcM8Y/byyN4ZJjnA2eo5fRbSRq9e0rwBdsIHEJGfr6JaE6sc aqVTeg3a2xhHNULbIaKI0dO4Y3jHbe6f0+kJYsgCc8rTUY7GR4j9nbRqj/0Y+GhL9E OYZIz06zraKD/O3RFbAeRmK9cT4LZLDK94XQX9k1FFcRa+Uf51iDWY/kuRE3196UIn 6rxXmoKSPcM0jLW70ZXbil31VeGvKLnvD/IaokGrSoiHrXLG5AsbsdnJj8xgBESFS1 DbaPN5zM4uxpVDsbJc9/rxdoEHuPTRRdRjo6HPTw7PcJJMznJhgYuGhrUyARQ/q9kJ eO/RW8co5jrDg== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id CB8D3D5B842; Mon, 15 Dec 2025 15:43:57 +0000 (UTC) From: Joel Granados Date: Mon, 15 Dec 2025 16:43:48 +0100 Subject: [PATCH] loadpin: Implement custom proc_handler for enforce Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251215-jag-const_loadpin-v1-1-6842775f4e90@kernel.org> X-B4-Tracking: v=1; b=H4sIALMsQGkC/x3MQQqAIBBA0avErBNUMqGrRIToWBOhoRGBePek5 Vv8XyBjIswwdQUSPpQphgbRd2B3EzZk5JpBcqmEFIodZmM2hnyvZzTuosD0KDxX0uvRDtC6K6G n93/OS60fj0rPCmMAAAA= X-Change-ID: 20251215-jag-const_loadpin-761f052f76c4 To: Kees Cook , Paul Moore , James Morris , "Serge E. Hallyn" Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Joel Granados X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=2223; i=joel.granados@kernel.org; h=from:subject:message-id; bh=2AxnBcqPgqXCnldBOy07VtuaCRIG8GxLYWiW94+3UqM=; b=owJ4nAHtARL+kA0DAAoBupfNUreWQU8ByyZiAGlALLxIt2tveNFT3YRDbt+neQRjc69SD6n9I S9XQDbETZnxFokBswQAAQoAHRYhBK5HCVcl5jElzssnkLqXzVK3lkFPBQJpQCy8AAoJELqXzVK3 lkFP2+wL/1ck/yY8LmBRUGMvwpAzd1p5neqnxyYSQ2FkjgFOUhPRkfOzCQpvkeJaeMX9rN5VAtV dQw3v7ccbroOolBMfNFuvtyVfzaxpOlKaJZpixsnrxr2lYBG55dPYYkpzpZAhSa1xTvrBg6FKkZ 9yPs3wRfBBv5/eSDETe3bnWf2whX+if378GgwSlF1ICy89S1jPlkvObV932KWMPwNbeG/a3VoCm Bd6vOUYdUlOtDcX4hSbIyAP8usOBvsMT9g0Lci9p1SpkR3Yg+SrGLL5YnlAkhxhnAkIriNDm8BP eQ4Mh0JN9lEhQtpkabSJ2GTZfeu+7mg1tdRFNAnhE7xT9lAqHxnZxH23q9SsIGt7aaYJdup9yuF OM8H1SLPPlrfTbD8DdEHpxefSAzE9CZ4P3vRhxvHZVr0vD7ghHqpf0TYe1QHqyodFkHG19h1Eh9 O/DIM7Q0qCYDPnjlw76E697PrfBbyBFCBRoDmQ1HdVqq8v39oz7bSEyEEbQMxSg3rBLg2udGL85 Rk= X-Developer-Key: i=joel.granados@kernel.org; a=openpgp; fpr=F1F8E46D30F0F6C4A45FF4465895FAAC338C6E77 X-Endpoint-Received: by B4 Relay for joel.granados@kernel.org/default with auth_id=239 The new proc_handler_loadpin returns -EINVAL when is_loadpin_writable is false and the kernel var (enforce) is being written. Move loadpin_sysctl_table to .rodata (by const qualifying it) as there is no need to change the value of the extra1 entry. Signed-off-by: Joel Granados --- Const qualifying ctl tables is part of the hardening effort in the linux kernel. --- security/loadpin/loadpin.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c index 273ffbd6defe1324d6688dec5f9fe6c9401283ed..f049c81b82a78265b6ae358bb2a= 814265cec9f16 100644 --- a/security/loadpin/loadpin.c +++ b/security/loadpin/loadpin.c @@ -53,18 +53,29 @@ static bool deny_reading_verity_digests; #endif =20 #ifdef CONFIG_SYSCTL -static struct ctl_table loadpin_sysctl_table[] =3D { +static bool is_loadpin_writable; + +static int proc_handler_loadpin(const struct ctl_table *table, int dir, + void *buffer, size_t *lenp, loff_t *ppos) +{ + if (!is_loadpin_writable && SYSCTL_USER_TO_KERN(dir)) + return -EINVAL; + return proc_dointvec_minmax(table, dir, buffer, lenp, ppos); +} + +static const struct ctl_table loadpin_sysctl_table[] =3D { { .procname =3D "enforce", .data =3D &enforce, .maxlen =3D sizeof(int), .mode =3D 0644, - .proc_handler =3D proc_dointvec_minmax, - .extra1 =3D SYSCTL_ONE, + .proc_handler =3D proc_handler_loadpin, + .extra1 =3D SYSCTL_ZERO, .extra2 =3D SYSCTL_ONE, }, }; =20 + static void set_sysctl(bool is_writable) { /* @@ -72,9 +83,9 @@ static void set_sysctl(bool is_writable) * device, allow sysctl to change modes for testing. */ if (is_writable) - loadpin_sysctl_table[0].extra1 =3D SYSCTL_ZERO; + is_loadpin_writable =3D true; else - loadpin_sysctl_table[0].extra1 =3D SYSCTL_ONE; + is_loadpin_writable =3D false; } #else static inline void set_sysctl(bool is_writable) { } --- base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8 change-id: 20251215-jag-const_loadpin-761f052f76c4 Best regards, --=20 Joel Granados