much like /proc/sys/kernel/modules_disable is used to disable module loading, /proc/sys/kernel/kexec_disable is used to disable kexec code loading. It would still be possible to use kexec -l to load a kernel, set the tunable to 1 so the kernel waiting to boot couldn't change, and then launch the kernel at a later time (through kexec -e or through a crash)
Signed-off-by: Eric Paris <[email protected]> --- include/linux/kexec.h | 2 ++ kernel/kexec.c | 4 ++++ kernel/sysctl.c | 13 +++++++++++++ 3 files changed, 19 insertions(+), 0 deletions(-) diff --git a/include/linux/kexec.h b/include/linux/kexec.h index 03e8e8d..fd8b2b8 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -195,6 +195,8 @@ extern struct kimage *kexec_crash_image; #define VMCOREINFO_NOTE_SIZE (KEXEC_NOTE_HEAD_BYTES*2 + VMCOREINFO_BYTES \ + VMCOREINFO_NOTE_NAME_BYTES) +extern int kexec_load_disabled; + /* Location of a reserved region to hold the crash kernel. */ extern struct resource crashk_res; diff --git a/kernel/kexec.c b/kernel/kexec.c index 213ce69..5aff5cd 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -48,6 +48,7 @@ static unsigned char vmcoreinfo_data[VMCOREINFO_BYTES]; u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4]; size_t vmcoreinfo_size; size_t vmcoreinfo_max_size = sizeof(vmcoreinfo_data); +int kexec_load_disabled; /* Location of the reserved area for the crash kernel */ struct resource crashk_res = { @@ -949,6 +950,9 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, !capable(CAP_SYS_MODULE)) return -EPERM; + if (kexec_load_disabled) + return -EPERM; + /* * Verify we have a legal set of flags * This leaves us room for future extensions. diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 0e1ac51..1fdc973 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -55,6 +55,7 @@ #include <linux/kprobes.h> #include <linux/pipe_fs_i.h> #include <linux/oom.h> +#include <linux/kexec.h> #include <asm/uaccess.h> #include <asm/processor.h> @@ -569,6 +570,18 @@ static struct ctl_table kern_table[] = { .extra2 = &one, }, #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_HOTPLUG { .procname = "hotplug", _______________________________________________ kexec mailing list [email protected] http://lists.infradead.org/mailman/listinfo/kexec
