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

[Tushar Sugandhi <tusharsu@linux.microsoft.com>]

On 7/11/23 18:28, RuiRui Yang wrote:
> On Wed, 12 Jul 2023 at 03:15, Tushar Sugandhi
> <tusharsu@linux.microsoft.com> wrote:
>>
>> On 7/7/23 01:20, RuiRui Yang wrote:
>>> On Tue, 4 Jul 2023 at 05:58, Tushar Sugandhi
>>> <tusharsu@linux.microsoft.com> 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@linux.microsoft.com>
>>>> ---
>>>>    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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>>>> kexec@lists.infradead.org
>>>> http://lists.infradead.org/mailman/listinfo/kexec
>>>>

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