From: Eric Biggers <ebiggers@xxxxxxxxxx> 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. Cc: Alexei Starovoitov <ast@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> 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: Eric Biggers <ebiggers@xxxxxxxxxx> --- Documentation/admin-guide/sysctl/kernel.rst | 25 ++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index def074807cee9..454f3402ed321 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -49,7 +49,7 @@ show up in /proc/sys/kernel: - kexec_load_disabled - kptr_restrict - l2cr [ PPC only ] -- modprobe ==> Documentation/debugging-modules.txt +- modprobe - modules_disabled - msg_next_id [ sysv ipc ] - msgmax @@ -444,6 +444,29 @@ l2cr: (PPC only) This flag controls the L2 cache of G3 processor boards. If 0, the cache is disabled. Enabled if nonzero. +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 "foo" to mount(), then the kernel will automatically +request the module "fs-foo.ko" 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. + +Also see Documentation/debugging-modules.txt. modules_disabled: ================= -- 2.25.1
