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?
-Kees
--
Kees Cook
Chrome OS Security
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