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* [PATCH] kexec: include sysctl to disable
@ 2011-01-19 22:26 Eric Paris
2011-01-20 5:21 ` WANG Cong
0 siblings, 1 reply; 6+ messages in thread
From: Eric Paris @ 2011-01-19 22:26 UTC (permalink / raw)
To: linux-kernel, kexec; +Cc: ebiederm
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 <eparis@redhat.com>
---
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",
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] kexec: include sysctl to disable
2011-01-19 22:26 [PATCH] kexec: include sysctl to disable Eric Paris
@ 2011-01-20 5:21 ` WANG Cong
2011-01-20 5:32 ` WANG Cong
0 siblings, 1 reply; 6+ messages in thread
From: WANG Cong @ 2011-01-20 5:21 UTC (permalink / raw)
To: linux-kernel; +Cc: kexec
On Wed, 19 Jan 2011 17:26:30 -0500, Eric Paris wrote:
> 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)
>
But root can still change it to 0 and do kexec like normal, right?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] kexec: include sysctl to disable
2011-01-20 5:21 ` WANG Cong
@ 2011-01-20 5:32 ` WANG Cong
2011-01-27 18:40 ` Eric Paris
0 siblings, 1 reply; 6+ messages in thread
From: WANG Cong @ 2011-01-20 5:32 UTC (permalink / raw)
To: linux-kernel; +Cc: kexec
On Thu, 20 Jan 2011 05:21:50 +0000, WANG Cong wrote:
> On Wed, 19 Jan 2011 17:26:30 -0500, Eric Paris wrote:
>
>> 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)
>>
>>
> But root can still change it to 0 and do kexec like normal, right?
Er... never mind, it is a one-way road...
Looks like a good balance between reusing CAP_SYS_MODULE and introducing
a new CAP_SYS_XXX.
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Thanks.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] kexec: include sysctl to disable
2011-01-20 5:32 ` WANG Cong
@ 2011-01-27 18:40 ` Eric Paris
2011-01-27 18:50 ` Vivek Goyal
2011-01-27 18:56 ` Neil Horman
0 siblings, 2 replies; 6+ messages in thread
From: Eric Paris @ 2011-01-27 18:40 UTC (permalink / raw)
To: WANG Cong, Eric Paris; +Cc: linux-kernel, kexec, Eric W. Biederman
Ping, not hearing any argument is usually a good thing :)
-Eric
On Thu, Jan 20, 2011 at 12:32 AM, WANG Cong <xiyou.wangcong@gmail.com> wrote:
>> On Wed, 19 Jan 2011 17:26:30 -0500, Eric Paris wrote:
>>
>>> 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)
> Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] kexec: include sysctl to disable
2011-01-27 18:40 ` Eric Paris
@ 2011-01-27 18:50 ` Vivek Goyal
2011-01-27 18:56 ` Neil Horman
1 sibling, 0 replies; 6+ messages in thread
From: Vivek Goyal @ 2011-01-27 18:50 UTC (permalink / raw)
To: Eric Paris; +Cc: WANG Cong, Eric Paris, linux-kernel, kexec, Eric W. Biederman
On Thu, Jan 27, 2011 at 01:40:02PM -0500, Eric Paris wrote:
> Ping, not hearing any argument is usually a good thing :)
>
So if we allowing locking down module loading, why not allow locking down
kexec kernel loading, hence...
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Vivek
> -Eric
>
> On Thu, Jan 20, 2011 at 12:32 AM, WANG Cong <xiyou.wangcong@gmail.com> wrote:
>
> >> On Wed, 19 Jan 2011 17:26:30 -0500, Eric Paris wrote:
> >>
> >>> 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)
>
> > Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
> --
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] kexec: include sysctl to disable
2011-01-27 18:40 ` Eric Paris
2011-01-27 18:50 ` Vivek Goyal
@ 2011-01-27 18:56 ` Neil Horman
1 sibling, 0 replies; 6+ messages in thread
From: Neil Horman @ 2011-01-27 18:56 UTC (permalink / raw)
To: Eric Paris; +Cc: WANG Cong, Eric Paris, kexec, linux-kernel, Eric W. Biederman
On Thu, Jan 27, 2011 at 01:40:02PM -0500, Eric Paris wrote:
> Ping, not hearing any argument is usually a good thing :)
>
> -Eric
>
> On Thu, Jan 20, 2011 at 12:32 AM, WANG Cong <xiyou.wangcong@gmail.com> wrote:
>
> >> On Wed, 19 Jan 2011 17:26:30 -0500, Eric Paris wrote:
> >>
> >>> 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)
>
> > Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
>
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2011-01-27 18:56 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2011-01-19 22:26 [PATCH] kexec: include sysctl to disable Eric Paris
2011-01-20 5:21 ` WANG Cong
2011-01-20 5:32 ` WANG Cong
2011-01-27 18:40 ` Eric Paris
2011-01-27 18:50 ` Vivek Goyal
2011-01-27 18:56 ` Neil Horman
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