Re: [PATCH 10/10] kexec: update kexec_file_load syscall to call ima_kexec_post_load

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On 7/11/23 18:28, RuiRui Yang wrote:
On Wed, 12 Jul 2023 at 03:15, Tushar Sugandhi
<tusharsu@xxxxxxxxxxxxxxxxxxx> wrote:

On 7/7/23 01:20, RuiRui Yang wrote:
On Tue, 4 Jul 2023 at 05:58, Tushar Sugandhi
<tusharsu@xxxxxxxxxxxxxxxxxxx> wrote:
The kexec_file_load syscall is used to load a new kernel for kexec.
The syscall needs to update its function to call ima_kexec_post_load, which
was implemented in a previous patch.  ima_kexec_post_load takes care of
mapping the measurement list for the next kernel and registering a reboot
notifier if it's not already registered.

Modify the kexec_file_load syscall to call ima_kexec_post_load after the
image has been loaded and prepared for kexec.  This ensures that the IMA
measurement list will be available to the next kernel after a kexec reboot.
This also ensures the measurements taken in the window between kexec load
and execute are captured and passed to the next kernel.

Declare the kimage_file_post_load function in the kernel/kexec_internal.h,
so it can be properly used in the syscall.

Signed-off-by: Tushar Sugandhi <tusharsu@xxxxxxxxxxxxxxxxxxx>
---
   kernel/kexec_file.c     | 7 +++++++
   kernel/kexec_internal.h | 1 +
   2 files changed, 8 insertions(+)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index f989f5f1933b..efe28e77280c 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -184,6 +184,11 @@ kimage_validate_signature(struct kimage *image)
   }
   #endif

+void kimage_file_post_load(struct kimage *image)
+{
+       ima_kexec_post_load(image);
+}
+
   /*
    * In file mode list of segments is prepared by kernel. Copy relevant
    * data from user space, do error checking, prepare segment list
@@ -399,6 +404,8 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,

          kimage_terminate(image);

+       kimage_file_post_load(image);
I think it should be only done for the reboot case,  please just
exclude the kdump case here..

Thanks for the feedback RuiRui.  Appreciate it.

Conceptually I agree with you that this needs to be done only for reboot.
I need to figure out how to do it implementation wise.

If you can give me pointers/suggestions, that would help.
Hi Tushar,

You can check the flags argument in the function
if (flags & KEXEC_FILE_ON_CRASH) is true then this is a kdump kernel
loading, just skip the kimage_file_post_load in that case?
Great.  Thanks for the pointer.  Will do.
~Tushar
~Tushar
+
          ret = machine_kexec_post_load(image);
          if (ret)
                  goto out;
diff --git a/kernel/kexec_internal.h b/kernel/kexec_internal.h
index 74da1409cd14..98dd5fcafaf0 100644
--- a/kernel/kexec_internal.h
+++ b/kernel/kexec_internal.h
@@ -30,6 +30,7 @@ static inline void kexec_unlock(void)

   #ifdef CONFIG_KEXEC_FILE
   #include <linux/purgatory.h>
+void kimage_file_post_load(struct kimage *image);
   void kimage_file_post_load_cleanup(struct kimage *image);
   extern char kexec_purgatory[];
   extern size_t kexec_purgatory_size;
--
2.25.1


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