diff options
| -rw-r--r-- | Documentation/sysctl/kernel.txt | 15 | ||||
| -rw-r--r-- | include/linux/kexec.h | 1 | ||||
| -rw-r--r-- | kernel/kexec.c | 3 | ||||
| -rw-r--r-- | kernel/sysctl.c | 13 |
4 files changed, 30 insertions, 2 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 6d486404200e..ee9a2f983b99 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -33,6 +33,7 @@ show up in /proc/sys/kernel: - domainname - hostname - hotplug +- kexec_load_disabled - kptr_restrict - kstack_depth_to_print [ X86 only ] - l2cr [ PPC only ] @@ -287,6 +288,18 @@ Default value is "/sbin/hotplug". ============================================================== +kexec_load_disabled: + +A toggle indicating if the kexec_load syscall has been disabled. This +value defaults to 0 (false: kexec_load enabled), but can be set to 1 +(true: kexec_load disabled). Once true, kexec can no longer be used, and +the toggle cannot be set back to false. This allows a kexec image to be +loaded before disabling the syscall, allowing a system to set up (and +later use) an image without it being altered. Generally used together +with the "modules_disabled" sysctl. + +============================================================== + kptr_restrict: This toggle indicates whether restrictions are placed on @@ -331,7 +344,7 @@ A toggle value indicating if modules are allowed to be loaded in an otherwise modular kernel. This toggle defaults to off (0), but can be set true (1). Once true, modules can be neither loaded nor unloaded, and the toggle cannot be set back -to false. +to false. Generally used with the "kexec_load_disabled" toggle. ============================================================== diff --git a/include/linux/kexec.h b/include/linux/kexec.h index 5fd33dc1fe3a..6d4066cdb5b5 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -170,6 +170,7 @@ unsigned long paddr_vmcoreinfo_note(void); extern struct kimage *kexec_image; extern struct kimage *kexec_crash_image; +extern int kexec_load_disabled; #ifndef kexec_flush_icache_page #define kexec_flush_icache_page(page) diff --git a/kernel/kexec.c b/kernel/kexec.c index 9c970167e402..ac738781d356 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -932,6 +932,7 @@ static int kimage_load_segment(struct kimage *image, */ struct kimage *kexec_image; struct kimage *kexec_crash_image; +int kexec_load_disabled; static DEFINE_MUTEX(kexec_mutex); @@ -942,7 +943,7 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, int result; /* We only trust the superuser with rebooting the system. */ - if (!capable(CAP_SYS_BOOT)) + if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) return -EPERM; /* diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 693eac39c202..096db7452cbd 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -62,6 +62,7 @@ #include <linux/capability.h> #include <linux/binfmts.h> #include <linux/sched/sysctl.h> +#include <linux/kexec.h> #include <asm/uaccess.h> #include <asm/processor.h> @@ -614,6 +615,18 @@ static struct ctl_table kern_table[] = { .proc_handler = proc_dointvec, }, #endif +#ifdef CONFIG_KEXEC + { + .procname = "kexec_load_disabled", + .data = &kexec_load_disabled, + .maxlen = sizeof(int), + .mode = 0644, + /* only handle a transition from default "0" to "1" */ + .proc_handler = proc_dointvec_minmax, + .extra1 = &one, + .extra2 = &one, + }, +#endif #ifdef CONFIG_MODULES { .procname = "modprobe", |