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Fri, 15 May 2026 10:20:35 -0700 (PDT) From: Michal Gorlas Date: Fri, 15 May 2026 19:20:19 +0200 Subject: [PATCH 1/2] module: add CONFIG_MODULE_RESTRICT_AUTOLOAD 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: <20260515-autoload_restrict-v1-1-40b7c03ddd04@9elements.com> References: <20260515-autoload_restrict-v1-0-40b7c03ddd04@9elements.com> In-Reply-To: <20260515-autoload_restrict-v1-0-40b7c03ddd04@9elements.com> To: Jonathan Corbet , Shuah Khan , Luis Chamberlain , Petr Pavlu , Daniel Gomez , Sami Tolvanen , Aaron Tomlin Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-modules@vger.kernel.org, Michal Gorlas X-Mailer: b4 0.15.0 Add CONFIG_MODULE_RESTRICT_AUTOLOAD and modrestrict parameter documentation. Signed-off-by: Michal Gorlas --- Documentation/admin-guide/kernel-parameters.txt | 5 +++++ kernel/module/Kconfig | 15 +++++++++++++++ 2 files changed, 20 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index 03a550630644..1013104f0943 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4185,6 +4185,11 @@ Kernel parameters For details see: Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst =20 + modrestrict=3D + Control the restriction of module auto-loading to + CAP_SYS_ADMIN. If no value is specified, this + is set to the value of CONFIG_MODULE_RESTRICT_AUTOLOAD. + .async_probe[=3D] [KNL] If no value is specified or if the value specified is not a valid , enable asynchronous diff --git a/kernel/module/Kconfig b/kernel/module/Kconfig index 43b1bb01fd27..c9e01bb848c0 100644 --- a/kernel/module/Kconfig +++ b/kernel/module/Kconfig @@ -337,6 +337,21 @@ config MODULE_SIG_HASH =20 endif # MODULE_SIG || IMA_APPRAISE_MODSIG =20 +config MODULE_RESTRICT_AUTOLOAD + bool "Restrict module auto-loading to privileged users" + default n + help + Restrict module auto-loading in response to use of some feature + implemented by an unloaded module to CAP_SYS_ADMIN. Enabling this + option helps reducing the attack surface where unprivileged users + can abuse auto-loading to cause a vulnerable module to load that is + then exploited. + + Note that this option also prevents a benign use of auto-loading for + a non-root users. Thus if enabled, the root user should execute + modprobe manually if needed, or add the module to the list of modules + loaded at the boot by modifying init scripts. + config MODULE_COMPRESS bool "Module compression" help --=20 2.54.0 From nobody Mon May 25 08:11:54 2026 Received: from mail-wm1-f46.google.com (mail-wm1-f46.google.com [209.85.128.46]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C52343DA5D0 for ; Fri, 15 May 2026 17:20:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.46 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778865640; cv=none; b=Z9lEwSZSdt9bULaXPMdbU4MieFE9XEfkOLMfqW7cGUw4BCgUTAKGwRD3B+fN60acd76hU/AXT/glGN6cYz/Kk85kSoQspBDft5GQ5S4FLSM8ySF0oK/RPlFSWtfBIyNXFxwrx1iFpwMrpeA3FQDUqA72Bc40+BB2p4pYI2aCkeo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; 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Fri, 15 May 2026 10:20:36 -0700 (PDT) Received: from [192.168.2.212] ([185.209.196.194]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48fe537ccf5sm77251515e9.14.2026.05.15.10.20.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 May 2026 10:20:36 -0700 (PDT) From: Michal Gorlas Date: Fri, 15 May 2026 19:20:20 +0200 Subject: [PATCH 2/2] module: restrict autoload to CAP_SYS_ADMIN if CONFIG_MODULE_RESTRICT_AUTOLOAD 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: <20260515-autoload_restrict-v1-2-40b7c03ddd04@9elements.com> References: <20260515-autoload_restrict-v1-0-40b7c03ddd04@9elements.com> In-Reply-To: <20260515-autoload_restrict-v1-0-40b7c03ddd04@9elements.com> To: Jonathan Corbet , Shuah Khan , Luis Chamberlain , Petr Pavlu , Daniel Gomez , Sami Tolvanen , Aaron Tomlin Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-modules@vger.kernel.org, Michal Gorlas X-Mailer: b4 0.15.0 Restrict module auto-loading to CAP_SYS_ADMIN if CONFIG_MODULE_RESTRICT_AUTOLOAD is enabled, cmdline parameter modrestrict=3Dtrue, or kernel.modrestrict=3D1 is set with sysctl. Signed-off-by: Michal Gorlas --- kernel/module/internal.h | 1 + kernel/module/kmod.c | 5 +++++ kernel/module/main.c | 11 +++++++++++ 3 files changed, 17 insertions(+) diff --git a/kernel/module/internal.h b/kernel/module/internal.h index 061161cc79d9..496d8703f0c6 100644 --- a/kernel/module/internal.h +++ b/kernel/module/internal.h @@ -46,6 +46,7 @@ struct kernel_symbol { =20 extern struct mutex module_mutex; extern struct list_head modules; +extern bool module_autoload_restrict; =20 extern const struct module_attribute *const modinfo_attrs[]; extern const size_t modinfo_attrs_count; diff --git a/kernel/module/kmod.c b/kernel/module/kmod.c index a25dccdf7aa7..58b28c23f571 100644 --- a/kernel/module/kmod.c +++ b/kernel/module/kmod.c @@ -156,6 +156,11 @@ int __request_module(bool wait, const char *fmt, ...) if (ret) return ret; =20 + if (module_autoload_restrict && !capable(CAP_SYS_ADMIN)) { + pr_alert("denied attempt to auto-load module %s\n", module_name); + return -EPERM; + } + ret =3D down_timeout(&kmod_concurrent_max, MAX_KMOD_ALL_BUSY_TIMEOUT * HZ= ); if (ret) { pr_warn_ratelimited("request_module: modprobe %s cannot be processed, km= od busy with %d threads for more than %d seconds now", diff --git a/kernel/module/main.c b/kernel/module/main.c index 46dd8d25a605..a293b75ce9b7 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -130,6 +130,10 @@ static void mod_update_bounds(struct module *mod) static int modules_disabled; core_param(nomodule, modules_disabled, bint, 0); =20 +/* Restrict auto-loading? */ +bool module_autoload_restrict =3D IS_ENABLED(CONFIG_MODULE_RESTRICT_AUTOLO= AD); +core_param(modrestrict, module_autoload_restrict, bool, 0); + static const struct ctl_table module_sysctl_table[] =3D { { .procname =3D "modprobe", @@ -148,6 +152,13 @@ static const struct ctl_table module_sysctl_table[] = =3D { .extra1 =3D SYSCTL_ONE, .extra2 =3D SYSCTL_ONE, }, + { + .procname =3D "modrestrict", + .data =3D &module_autoload_restrict, + .maxlen =3D sizeof(bool), + .mode =3D 0644, + .proc_handler =3D proc_dobool, + }, }; =20 static int __init init_module_sysctl(void) --=20 2.54.0