[Cc'ing linux-security-module, linux-integrity]
On Thu, 2020-05-07 at 17:27 -0700, Scott Branden wrote:
> Add kernel_pread_file* support to kernel to allow for partial read
> of files with an offset into the file. Existing kernel_read_file
> functions call new kernel_pread_file functions with offset=0 and
> flags=KERNEL_PREAD_FLAG_WHOLE.
>
> Signed-off-by: Scott Branden <[email protected]>
> ---
<snip>
> @@ -941,14 +955,16 @@ int kernel_read_file(struct file *file, void **buf,
> loff_t *size,
>
> if (bytes == 0)
> break;
> +
> + buf_pos += bytes;
> }
>
> - if (pos != i_size) {
> + if (pos != read_end) {
> ret = -EIO;
> goto out_free;
> }
>
> - ret = security_kernel_post_read_file(file, *buf, i_size, id);
> + ret = security_kernel_post_read_file(file, *buf, alloc_size, id);
> if (!ret)
> *size = pos;
Prior to the patch set that introduced this security hook, firmware
would be read twice, once for measuring/appraising the firmware and
again reading the file contents into memory. Partial reads will break
both IMA's measuring the file and appraising the file signatures.
Mimi
