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Serge E. Hallyn wrote:
> Andrew, I've cc:d you here bc in doing this patch I noticed that your
> 64-bit capabilities patch switched this code from an explicit check
> of cap_t(p->cap_effective) to using __capable(). That means that
> now being glossed over by the oom killer means PF_SUPERPRIV will
> be set. Is that intentional?
Yes, I switched the check because the old one didn't work with the new
capability representation.
However, I had not thought this aspect of this replacement through. At
the time, it seemed obvious but in this case it actually depends on
whether you think using privilege (PF_SUPERPRIV) means "benefited from
privilege", or "successfully completed a privileged operation".
I suspect, in this case, the correct thing to do is add the equivalent of:
#define CAPABLE_PROBE_ONLY(a,b) (!security_capable(a,b))
and use that in the code in question. That is, return to the old
behavior in a way that will not break if we ever need to add more bits.
Thanks for finding this.
Cheers
Andrew
>
> Signed-off-by: Serge Hallyn <[email protected]>
> ---
> mm/oom_kill.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 016127e..9fd8d5d 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -128,7 +128,7 @@ unsigned long badness(struct task_struct *p, unsigned long uptime,
> * Superuser processes are usually more important, so we make it
> * less likely that we kill those.
> */
> - if (__capable(p, CAP_SYS_ADMIN) || p->uid == 0 || p->euid == 0)
> + if (__capable(p, CAP_SYS_ADMIN) || __capable(p, CAP_SYS_RESOURCE))
> points /= 4;
>
> /*
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