On 03/17/25 at 06:04pm, steven chen wrote:
> Carrying the IMA measurement list across kexec requires allocating a
> buffer and copying the measurement records. Separate allocating the
> buffer and copying the measurement records into separate functions in
> order to allocate the buffer at kexec 'load' and copy the measurements
> at kexec 'execute'.
>
> This patch includes the following changes:
> - Refactor ima_dump_measurement_list() to move the memory allocation
> to a separate function ima_alloc_kexec_file_buf() which allocates
> buffer of size 'kexec_segment_size' at kexec 'load'.
> - Make the local variable ima_kexec_file in ima_dump_measurement_list()
> a local static to the file, so that it can be accessed from
> ima_alloc_kexec_file_buf().
> - Make necessary changes to the function ima_add_kexec_buffer() to call
> the above two functions.
We may not need above details about code change because it's not so
difficult to get them from patch.
>
> Signed-off-by: Tushar Sugandhi <tusharsu@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: steven chen <chenste@xxxxxxxxxxxxxxxxxxx>
> ---
> security/integrity/ima/ima_kexec.c | 67 +++++++++++++++++++++++++-----
> 1 file changed, 56 insertions(+), 11 deletions(-)
>
> diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
> index 8567619889d1..45170e283272 100644
> --- a/security/integrity/ima/ima_kexec.c
> +++ b/security/integrity/ima/ima_kexec.c
> @@ -15,6 +15,48 @@
> #include "ima.h"
>
> #ifdef CONFIG_IMA_KEXEC
> +static struct seq_file ima_kexec_file;
> +
> +static void ima_reset_kexec_file(struct seq_file *sf)
> +{
> + sf->buf = NULL;
> + sf->size = 0;
> + sf->read_pos = 0;
> + sf->count = 0;
> +}
> +
> +static void ima_free_kexec_file_buf(struct seq_file *sf)
> +{
> + vfree(sf->buf);
> + ima_reset_kexec_file(sf);
> +}
> +
> +static int ima_alloc_kexec_file_buf(size_t segment_size)
> +{
> + /*
> + * kexec 'load' may be called multiple times.
> + * Free and realloc the buffer only if the segment_size is
> + * changed from the previous kexec 'load' call.
> + */
> + if (ima_kexec_file.buf && ima_kexec_file.size == segment_size)
> + goto out;
> +
> + ima_free_kexec_file_buf(&ima_kexec_file);
> +
> + /* segment size can't change between kexec load and execute */
> + ima_kexec_file.buf = vmalloc(segment_size);
> + if (!ima_kexec_file.buf)
> + return -ENOMEM;
> +
> + ima_kexec_file.size = segment_size;
> +
> +out:
> + ima_kexec_file.read_pos = 0;
> + ima_kexec_file.count = sizeof(struct ima_kexec_hdr); /* reserved space */
> +
> + return 0;
> +}
> +
> /*
> * Copy the measurement list to the allocated memory
> * compare the size of IMA measurement list with the size of the allocated memory
> @@ -26,23 +68,16 @@
> static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
> unsigned long segment_size)
> {
> - struct seq_file ima_kexec_file;
> struct ima_queue_entry *qe;
> struct ima_kexec_hdr khdr;
> int ret = 0;
>
> /* segment size can't change between kexec load and execute */
> - ima_kexec_file.buf = vmalloc(segment_size);
> if (!ima_kexec_file.buf) {
> - ret = -ENOMEM;
> - goto out;
> + pr_err("Kexec file buf not allocated\n");
> + return -EINVAL;
> }
>
> - ima_kexec_file.file = NULL;
> - ima_kexec_file.size = segment_size;
> - ima_kexec_file.read_pos = 0;
> - ima_kexec_file.count = sizeof(khdr); /* reserved space */
> -
> memset(&khdr, 0, sizeof(khdr));
> khdr.version = 1;
> /* This is an append-only list, no need to hold the RCU read lock */
> @@ -79,8 +114,6 @@ static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
> *buffer_size = ima_kexec_file.count;
> *buffer = ima_kexec_file.buf;
> out:
> - if (ret == -EINVAL)
> - vfree(ima_kexec_file.buf);
> return ret;
> }
>
> @@ -119,6 +152,12 @@ void ima_add_kexec_buffer(struct kimage *image)
> return;
> }
>
> + ret = ima_alloc_kexec_file_buf(kexec_segment_size);
> + if (ret < 0) {
> + pr_err("Not enough memory for the kexec measurement buffer.\n");
> + return;
> + }
> +
> ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer,
> kexec_segment_size);
> if (!kexec_buffer) {
> @@ -140,6 +179,12 @@ void ima_add_kexec_buffer(struct kimage *image)
> image->ima_buffer_size = kexec_segment_size;
> image->ima_buffer = kexec_buffer;
>
> + /*
> + * kexec owns kexec_buffer after kexec_add_buffer() is called
> + * and it will vfree() that buffer.
> + */
> + ima_reset_kexec_file(&ima_kexec_file);
I can't see why we need call ima_reset_kexec_file() here. If we need
reuse the buffer, we will reset the needed fields at the end of
ima_alloc_kexec_file_buf(). Not sure if I miss anything.
static int ima_alloc_kexec_file_buf(size_t segment_size)
{
......
out:
ima_kexec_file.read_pos = 0;
ima_kexec_file.count = sizeof(struct ima_kexec_hdr); /* reserved space */
return 0;
}
