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
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jeff Vander Stoep <jeffv@google.com>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: NeilBrown <neilb@suse.com>
Link: http://lkml.kernel.org/r/20200312202552.241885-4-ebiggers@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Eric Biggers 2020-04-10 14:33:50 -07:00 committed by Linus Torvalds
parent 26c5d78c97
commit 6e71582506

View file

@ -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
============