At Tue, 22 Jul 2014 10:39:00 -0700,
Kees Cook wrote:
>
> On Mon, Jul 21, 2014 at 11:55 PM, Takashi Iwai <ti...@suse.de> wrote:
> > At Mon, 21 Jul 2014 12:06:41 -0700,
> > Kees Cook wrote:
> >>
> >> This attaches LSM hooks to the existing firmware loading interfaces:
> >> filesystem-found firmware and demand-loaded blobs.
> >>
> >> Signed-off-by: Kees Cook <keesc...@chromium.org>
> >> Acked-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
> >> ---
> >> drivers/base/firmware_class.c | 16 ++++++++++++++--
> >> 1 file changed, 14 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> >> index d276e33880be..7399bab71ced 100644
> >> --- a/drivers/base/firmware_class.c
> >> +++ b/drivers/base/firmware_class.c
> >> @@ -28,6 +28,7 @@
> >> #include <linux/suspend.h>
> >> #include <linux/syscore_ops.h>
> >> #include <linux/reboot.h>
> >> +#include <linux/security.h>
> >>
> >> #include <generated/utsrelease.h>
> >>
> >> @@ -308,12 +309,17 @@ static int fw_read_file_contents(struct file *file,
> >> struct firmware_buf *fw_buf)
> >> if (rc != size) {
> >> if (rc > 0)
> >> rc = -EIO;
> >> - vfree(buf);
> >> - return rc;
> >> + goto fail;
> >> }
> >> + rc = security_kernel_fw_from_file(file, buf, size);
> >> + if (rc)
> >> + goto fail;
> >> fw_buf->data = buf;
> >> fw_buf->size = size;
> >> return 0;
> >> +fail:
> >> + vfree(buf);
> >> + return rc;
> >> }
> >>
> >> static int fw_get_filesystem_firmware(struct device *device,
> >> @@ -640,6 +646,12 @@ static ssize_t firmware_loading_store(struct device
> >> *dev,
> >> break;
> >> case 0:
> >> if (test_bit(FW_STATUS_LOADING, &fw_buf->status)) {
> >> + if (security_kernel_fw_from_file(NULL, fw_buf->data,
> >> + fw_buf->size)) {
> >> + fw_load_abort(fw_priv);
> >> + break;
> >> + }
> >> set_bit(FW_STATUS_DONE, &fw_buf->status);
> >> clear_bit(FW_STATUS_LOADING, &fw_buf->status);
> >
> > security_kernel_fw_from_file() should be called after
> > fw_map_pages_buf() call (that is found after these lines).
> > Otherwise fw_buf->buf won't contain a valid buffer pointer.
>
> Ah! Good to know. I guess I was getting lucky in my testing. Is this a
> race condition?
This is the code path where direct f/w loading fails but the
user-space helper feeds the data. Did you test that scenario?
Takashi
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