Re: [PATCH v2] crypto: ccp - Fix the INIT_EX data file open failure

[Tom Lendacky]

On 4/14/22 11:23, Jacky Li wrote:
> There are 2 common cases when INIT_EX data file might not be
> opened successfully and fail the sev initialization:
>
> 1. In user namespaces, normal user tasks (e.g. VMM) can change their
>     current->fs->root to point to arbitrary directories. While
>     init_ex_path is provided as a module param related to root file
>     system. Solution: use the root directory of init_task to avoid
>     accessing the wrong file.
>
> 2. Normal user tasks (e.g. VMM) don't have the privilege to access
>     the INIT_EX data file. Solution: open the file as root and
>     restore permissions immediately.
>
> Fixes: 3d725965f836 ("crypto: ccp - Add SEV_INIT_EX support")
> Signed-off-by: Jacky Li <jackyli@xxxxxxxxxx>
> Reviewed-by: Peter Gonda <pgonda@xxxxxxxxxx>

Looks good, just a quick question. Should there be any type of access 
checks before switching credentials? Should we check access to /dev/sev or 
such? Or is the capability to load the module enough?

Thanks,
Tom

> ---
> Changelog since v1:
> - Added Fixes tag and Reviewed-By tag.
>
>   drivers/crypto/ccp/sev-dev.c | 30 ++++++++++++++++++++++++++++--
>   1 file changed, 28 insertions(+), 2 deletions(-)