Currently, kexec_buf is placed in order which means for the same
machine, the info in the kexec_buf is always located at the same
position each time the machine is booted. This may cause a risk for
sensitive information like LUKS volume key. Now struct kexec_buf has a
new field random which indicates it's supposed to be placed in a random
position.
Suggested-by: Jan Pazdziora <[email protected]>
Signed-off-by: Coiby Xu <[email protected]>
---
include/linux/kexec.h | 4 ++++
kernel/kexec_file.c | 21 +++++++++++++++++++++
2 files changed, 25 insertions(+)
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index f0e9f8eda7a3..c45bfc727737 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -171,6 +171,7 @@ int kexec_image_post_load_cleanup_default(struct kimage *image);
* @buf_min: The buffer can't be placed below this address.
* @buf_max: The buffer can't be placed above this address.
* @top_down: Allocate from top of memory.
+ * @random: Place the buffer at a random position.
*/
struct kexec_buf {
struct kimage *image;
@@ -182,6 +183,9 @@ struct kexec_buf {
unsigned long buf_min;
unsigned long buf_max;
bool top_down;
+#ifdef CONFIG_CRASH_DUMP
+ bool random;
+#endif
};
int kexec_load_purgatory(struct kimage *image, struct kexec_buf *kbuf);
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 3d64290d24c9..f7538d8f67e0 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -25,6 +25,9 @@
#include <linux/elfcore.h>
#include <linux/kernel.h>
#include <linux/kernel_read_file.h>
+#ifdef CONFIG_CRASH_DUMP
+#include <linux/prandom.h>
+#endif
#include <linux/syscalls.h>
#include <linux/vmalloc.h>
#include "kexec_internal.h"
@@ -437,6 +440,18 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
return ret;
}
+#ifdef CONFIG_CRASH_DUMP
+static unsigned long kexec_random_start(unsigned long start, unsigned long end)
+{
+ unsigned long temp_start;
+ unsigned short i;
+
+ get_random_bytes(&i, sizeof(unsigned short));
+ temp_start = start + (end - start) / USHRT_MAX * i;
+ return temp_start;
+}
+#endif
+
static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
struct kexec_buf *kbuf)
{
@@ -445,6 +460,10 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
temp_end = min(end, kbuf->buf_max);
temp_start = temp_end - kbuf->memsz + 1;
+#ifdef CONFIG_CRASH_DUMP
+ if (kbuf->random)
+ temp_start = kexec_random_start(temp_start, temp_end);
+#endif
do {
/* align down start */
@@ -482,6 +501,8 @@ static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,
unsigned long temp_start, temp_end;
temp_start = max(start, kbuf->buf_min);
+ if (kbuf->random)
+ temp_start = kexec_random_start(temp_start, end);
do {
temp_start = ALIGN(temp_start, kbuf->buf_align);
--
2.45.1
Hi Coiby,
kernel test robot noticed the following build errors:
[auto build test ERROR on 8a92980606e3585d72d510a03b59906e96755b8a]
url: https://github.com/intel-lab-lkp/linux/commits/Coiby-Xu/kexec_file-allow-to-place-kexec_buf-randomly/20240607-203154
base: 8a92980606e3585d72d510a03b59906e96755b8a
patch link: https://lore.kernel.org/r/20240607122622.167228-2-coxu%40redhat.com
patch subject: [PATCH v5 1/7] kexec_file: allow to place kexec_buf randomly
config: parisc-allyesconfig (https://download.01.org/0day-ci/archive/20240608/[email protected]/config)
compiler: hppa-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240608/[email protected]/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
All errors (new ones prefixed by >>):
kernel/kexec_file.c: In function 'locate_mem_hole_bottom_up':
>> kernel/kexec_file.c:504:17: error: 'struct kexec_buf' has no member named 'random'
504 | if (kbuf->random)
| ^~
>> kernel/kexec_file.c:505:30: error: implicit declaration of function 'kexec_random_start' [-Werror=implicit-function-declaration]
505 | temp_start = kexec_random_start(temp_start, end);
| ^~~~~~~~~~~~~~~~~~
cc1: some warnings being treated as errors
vim +504 kernel/kexec_file.c
496
497 static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,
498 struct kexec_buf *kbuf)
499 {
500 struct kimage *image = kbuf->image;
501 unsigned long temp_start, temp_end;
502
503 temp_start = max(start, kbuf->buf_min);
> 504 if (kbuf->random)
> 505 temp_start = kexec_random_start(temp_start, end);
506
507 do {
508 temp_start = ALIGN(temp_start, kbuf->buf_align);
509 temp_end = temp_start + kbuf->memsz - 1;
510
511 if (temp_end > end || temp_end > kbuf->buf_max)
512 return 0;
513 /*
514 * Make sure this does not conflict with any of existing
515 * segments
516 */
517 if (kimage_is_destination_range(image, temp_start, temp_end)) {
518 temp_start = temp_start + PAGE_SIZE;
519 continue;
520 }
521
522 /* We found a suitable memory range */
523 break;
524 } while (1);
525
526 /* If we are here, we found a suitable memory range */
527 kbuf->mem = temp_start;
528
529 /* Success, stop navigating through remaining System RAM ranges */
530 return 1;
531 }
532
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Hi Coiby,
kernel test robot noticed the following build errors:
[auto build test ERROR on 8a92980606e3585d72d510a03b59906e96755b8a]
url: https://github.com/intel-lab-lkp/linux/commits/Coiby-Xu/kexec_file-allow-to-place-kexec_buf-randomly/20240607-203154
base: 8a92980606e3585d72d510a03b59906e96755b8a
patch link: https://lore.kernel.org/r/20240607122622.167228-2-coxu%40redhat.com
patch subject: [PATCH v5 1/7] kexec_file: allow to place kexec_buf randomly
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20240608/[email protected]/config)
compiler: clang version 18.1.5 (https://github.com/llvm/llvm-project 617a15a9eac96088ae5e9134248d8236e34b91b1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240608/[email protected]/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
All errors (new ones prefixed by >>):
>> kernel/kexec_file.c:504:12: error: no member named 'random' in 'struct kexec_buf'
504 | if (kbuf->random)
| ~~~~ ^
>> kernel/kexec_file.c:505:16: error: call to undeclared function 'kexec_random_start'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
505 | temp_start = kexec_random_start(temp_start, end);
| ^
2 errors generated.
vim +504 kernel/kexec_file.c
496
497 static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,
498 struct kexec_buf *kbuf)
499 {
500 struct kimage *image = kbuf->image;
501 unsigned long temp_start, temp_end;
502
503 temp_start = max(start, kbuf->buf_min);
> 504 if (kbuf->random)
> 505 temp_start = kexec_random_start(temp_start, end);
506
507 do {
508 temp_start = ALIGN(temp_start, kbuf->buf_align);
509 temp_end = temp_start + kbuf->memsz - 1;
510
511 if (temp_end > end || temp_end > kbuf->buf_max)
512 return 0;
513 /*
514 * Make sure this does not conflict with any of existing
515 * segments
516 */
517 if (kimage_is_destination_range(image, temp_start, temp_end)) {
518 temp_start = temp_start + PAGE_SIZE;
519 continue;
520 }
521
522 /* We found a suitable memory range */
523 break;
524 } while (1);
525
526 /* If we are here, we found a suitable memory range */
527 kbuf->mem = temp_start;
528
529 /* Success, stop navigating through remaining System RAM ranges */
530 return 1;
531 }
532
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
On Fri, Jun 07, 2024 at 08:26:11PM +0800, Coiby Xu wrote:
> Currently, kexec_buf is placed in order which means for the same
> machine, the info in the kexec_buf is always located at the same
> position each time the machine is booted. This may cause a risk for
> sensitive information like LUKS volume key. Now struct kexec_buf has a
> new field random which indicates it's supposed to be placed in a random
> position.
>
> Suggested-by: Jan Pazdziora <[email protected]>
> Signed-off-by: Coiby Xu <[email protected]>
> ---
> include/linux/kexec.h | 4 ++++
> kernel/kexec_file.c | 21 +++++++++++++++++++++
> 2 files changed, 25 insertions(+)
>
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index f0e9f8eda7a3..c45bfc727737 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -171,6 +171,7 @@ int kexec_image_post_load_cleanup_default(struct kimage *image);
> * @buf_min: The buffer can't be placed below this address.
> * @buf_max: The buffer can't be placed above this address.
> * @top_down: Allocate from top of memory.
> + * @random: Place the buffer at a random position.
> */
> struct kexec_buf {
> struct kimage *image;
> @@ -182,6 +183,9 @@ struct kexec_buf {
> unsigned long buf_min;
> unsigned long buf_max;
> bool top_down;
> +#ifdef CONFIG_CRASH_DUMP
> + bool random;
> +#endif
Why is the ifdef needed?
> };
>
> int kexec_load_purgatory(struct kimage *image, struct kexec_buf *kbuf);
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index 3d64290d24c9..f7538d8f67e0 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -25,6 +25,9 @@
> #include <linux/elfcore.h>
> #include <linux/kernel.h>
> #include <linux/kernel_read_file.h>
> +#ifdef CONFIG_CRASH_DUMP
> +#include <linux/prandom.h>
> +#endif
No ifdef in .c files please. This should not be an issue.
> #include <linux/syscalls.h>
> #include <linux/vmalloc.h>
> #include "kexec_internal.h"
> @@ -437,6 +440,18 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
> return ret;
> }
>
> +#ifdef CONFIG_CRASH_DUMP
> +static unsigned long kexec_random_start(unsigned long start, unsigned long end)
> +{
> + unsigned long temp_start;
> + unsigned short i;
> +
> + get_random_bytes(&i, sizeof(unsigned short));
> + temp_start = start + (end - start) / USHRT_MAX * i;
> + return temp_start;
> +}
> +#endif
This #ifdef should be handled properly in the .h file.
> +
> static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
> struct kexec_buf *kbuf)
> {
> @@ -445,6 +460,10 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
>
> temp_end = min(end, kbuf->buf_max);
> temp_start = temp_end - kbuf->memsz + 1;
> +#ifdef CONFIG_CRASH_DUMP
> + if (kbuf->random)
> + temp_start = kexec_random_start(temp_start, temp_end);
> +#endif
Same with this.
And why do you need the boolean at all, why not just have
kexec_random_start() handle this properly for you?
thanks,
greg k-h