Re: [PATCH v5 1/7] fs: introduce kernel_pread_file* support

[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 scott.branden@broadcom.com

<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