Re: [Xen-devel] [PATCH] Fix boot crash on xsm/flask enabled builds when no policy module is present

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 26.08.13 at 12:03, Tomasz Wroblewski <tomasz.wroblewski@xxxxxxxxxx> 
>>> wrote:
> Xen crashes on boot of xsm/flask enabled builds, if policy module is not 
> specified.
> This seems to have worked on 4.1 at least.

Looking at the code (4.1.5) I can't see what would prevent the
same NULL pointer deref. Care to explain?

> Can be fixed by testing whether 
> policy_buffer
> is NULL before attempting to load from it - it's a global which is set to 
> non-NULL when
> policy module is detected.
> 
> Signed-off-by: Tomasz Wroblewski <tomasz.wroblewski@xxxxxxxxxx>
> ---
>  xen/xsm/flask/hooks.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
> index fa0589a..cfa2929 100644
> --- a/xen/xsm/flask/hooks.c
> +++ b/xen/xsm/flask/hooks.c
> @@ -1585,7 +1585,8 @@ static __init int flask_init(void)
>      if ( register_xsm(&flask_ops) )
>          panic("Flask: Unable to register with XSM.\n");
>  
> -    ret = security_load_policy(policy_buffer, policy_size);
> +    if ( policy_buffer )
> +        ret = security_load_policy(policy_buffer, policy_size);

Question is whether policy_buffer == NULL really isn't supposed
to result in a -E... return value (as in fact flask initialization failed).

Jan


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