Re: [PATCH 2/2] ima: Free IMA measurement buffer after kexec syscall

Tyler Hicks
2021-01-21T17:40:24Z

On 2021-01-21 09:30:03, Lakshmi Ramasubramanian wrote:
> IMA allocates kernel virtual memory to carry forward the measurement
> list, from the current kernel to the next kernel on kexec system call,
> in ima_add_kexec_buffer() function. This buffer is not freed before
> completing the kexec system call resulting in memory leak.
>
> Add ima_buffer field in "struct kimage" to store the virtual address
> of the buffer allocated for the IMA measurement list.
> Free the memory allocated for the IMA measurement list in
> kimage_file_post_load_cleanup() function.
>
> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> Suggested-by: Tyler Hicks <tyhicks@linux.microsoft.com>
> Fixes: 7b8589cc29e7 ("ima: on soft reboot, save the measurement list")

Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>

Tyler

> ---
> include/linux/kexec.h | 5 +++++
> kernel/kexec_file.c | 5 +++++
> security/integrity/ima/ima_kexec.c | 2 ++
> 3 files changed, 12 insertions(+)
>
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index 9e93bef52968..5f61389f5f36 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -300,6 +300,11 @@ struct kimage {
> /* Information for loading purgatory */
> struct purgatory_info purgatory_info;
> #endif
> +
> +#ifdef CONFIG_IMA_KEXEC
> + /* Virtual address of IMA measurement buffer for kexec syscall */
> + void *ima_buffer;
> +#endif
> };
>
> /* kexec interface functions */
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index b02086d70492..5c3447cf7ad5 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -166,6 +166,11 @@ void kimage_file_post_load_cleanup(struct kimage *image)
> vfree(pi->sechdrs);
> pi->sechdrs = NULL;
>
> +#ifdef CONFIG_IMA_KEXEC
> + vfree(image->ima_buffer);
> + image->ima_buffer = NULL;
> +#endif /* CONFIG_IMA_KEXEC */
> +
> /* See if architecture has anything to cleanup post load */
> arch_kimage_file_post_load_cleanup(image);
>
> diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
> index 212145008a01..8eadd0674629 100644
> --- a/security/integrity/ima/ima_kexec.c
> +++ b/security/integrity/ima/ima_kexec.c
> @@ -130,6 +130,8 @@ void ima_add_kexec_buffer(struct kimage *image)
> return;
> }
>
> + image->ima_buffer = kexec_buffer;
> +
> pr_debug("kexec measurement buffer for the loaded kernel at 0x%lx.\n",
> kbuf.mem);
> }
> --
> 2.30.0
>