Re: [PATCH] proc: don't show nonexistent capabilities (v2)

[Kees Cook]

On Sun, Oct 7, 2012 at 2:56 AM, Andrew Vagin <avagin@xxxxxxxxxx> wrote:
> Without this patch it is really hard to interpret a bounding set,
> if CAP_LAST_CAP is unknown for a current kernel.
>
> Non-existant capabilities can not be deleted from a bounding set
> with help of prctl.
>
> E.g.: Here are two examples without/with this patch.
> CapBnd: ffffffe0fdecffff
> CapBnd: 00000000fdecffff
>
> I suggest to hide non-existent capabilities. Here is two reasons.
> * It's logically and easier for using.
> * It helps to checkpoint-restore capabilities of tasks, because tasks
> can be restored on another kernel, where CAP_LAST_CAP is bigger.
>
> v2: Non-existent capabilities can not be removed from creds, because
>     in this case user cannot set all=eip. This patch cleans up non-existent
>     capabilities from content of /proc/pid/status
>
> Cc: Andrew G. Morgan <morgan@xxxxxxxxxx>
> Cc: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
> Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> Signed-off-by: Andrew Vagin <avagin@xxxxxxxxxx>

Seems sensible to me.

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees

-- 
Kees Cook
Chrome OS Security
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