From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: [patch 28/35] docs: admin-guide: document the kernel.modprobe sysctl Date: Fri, 10 Apr 2020 14:33:50 -0700 Message-ID: <20200410213350.o21mcrRmh%akpm@linux-foundation.org> References: <20200410143047.bf34a933ce1affdc042c7c80@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:48042 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726594AbgDJVdw (ORCPT ); Fri, 10 Apr 2020 17:33:52 -0400 In-Reply-To: <20200410143047.bf34a933ce1affdc042c7c80@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: akpm@linux-foundation.org, ast@kernel.org, ebiggers@google.com, gregkh@linuxfoundation.org, jeffv@google.com, jeyu@kernel.org, keescook@chromium.org, linux-mm@kvack.org, mcgrof@kernel.org, mm-commits@vger.kernel.org, neilb@suse.com, torvalds@linux-foundation.org From: Eric Biggers Subject: docs: admin-guide: document the kernel.modprobe sysctl Document the kernel.modprobe sysctl in the same place that all the other kernel.* sysctls are documented. Make sure to mention how to use this sysctl to completely disable module autoloading, and how this sysctl relates to CONFIG_STATIC_USERMODEHELPER. [ebiggers@google.com: v5] Link: http://lkml.kernel.org/r/20200318230515.171692-4-ebiggers@kernel.org Link: http://lkml.kernel.org/r/20200312202552.241885-4-ebiggers@kernel.org Signed-off-by: Eric Biggers Cc: Alexei Starovoitov Cc: Greg Kroah-Hartman Cc: Jeff Vander Stoep Cc: Jessica Yu Cc: Kees Cook Cc: Luis Chamberlain Cc: NeilBrown Signed-off-by: Andrew Morton --- Documentation/admin-guide/sysctl/kernel.rst | 21 ++++++++++++++++++ 1 file changed, 21 insertions(+) --- a/Documentation/admin-guide/sysctl/kernel.rst~docs-admin-guide-document-the-kernelmodprobe-sysctl +++ a/Documentation/admin-guide/sysctl/kernel.rst @@ -446,6 +446,27 @@ Notes: successful IPC object allocation. If an IPC object allocation syscall fails, it is undefined if the value remains unmodified or is reset to -1. +modprobe: +========= + +The path to the usermode helper for autoloading kernel modules, by +default "/sbin/modprobe". This binary is executed when the kernel +requests a module. For example, if userspace passes an unknown +filesystem type to mount(), then the kernel will automatically request +the corresponding filesystem module by executing this usermode helper. +This usermode helper should insert the needed module into the kernel. + +This sysctl only affects module autoloading. It has no effect on the +ability to explicitly insert modules. + +If this sysctl is set to the empty string, then module autoloading is +completely disabled. The kernel will not try to execute a usermode +helper at all, nor will it call the kernel_module_request LSM hook. + +If CONFIG_STATIC_USERMODEHELPER=y is set in the kernel configuration, +then the configured static usermode helper overrides this sysctl, +except that the empty string is still accepted to completely disable +module autoloading as described above. nmi_watchdog ============ _