From: Eric Biggers <ebiggers@xxxxxxxxxx> 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@xxxxxxxxxx: v5] Link: http://lkml.kernel.org/r/20200318230515.171692-4-ebiggers@xxxxxxxxxx Link: http://lkml.kernel.org/r/20200312202552.241885-4-ebiggers@xxxxxxxxxx Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> Cc: Alexei Starovoitov <ast@xxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Jeff Vander Stoep <jeffv@xxxxxxxxxx> Cc: Jessica Yu <jeyu@xxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx> Cc: NeilBrown <neilb@xxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- 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 ============ _
