linux-kernel - Re: [PATCH 5/6] file capabilities: remove needless inline functions

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Date:	Sat, 27 Sep 2008 08:40:07 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	"Andrew G. Morgan" <morgan@...nel.org>
Cc:	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [PATCH 5/6] file capabilities: remove needless inline functions

Quoting Andrew G. Morgan (morgan@...nel.org):
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> Serge,
> 
> I'd much rather simply remove the target argument from the
> security_capset_check() call. Relying on the caller to not do something

Yes, I did do that in a patch on top of all of these.  It increased the
kernel size by 8 (or was it 16) bytes :)  I assume that was because
now there were more references to 'current' which is inlined?  So I
should be able to fix that by saving current() away at the top of
the fn.

Will try that.

thanks,
-serge

> bad seems fragile... If the code internally operates on current only,
> then it doesn't need a target argument... No? (Evidently, such a change
> is also needed to selinux_capset_check() too, but this doesn't look like
> it will pose a problem for the selinux code.)
> 
> Cheers
> 
> Andrew
> 
> Serge E. Hallyn wrote:
> > cap_limit_ptraced_target always returns 1, so nix it.
> > 
> > cap_block_setpcap can't return 1 any more, because
> > kernel/capabilities.c:sys_capset() will return -EPERM
> > if it is called on a task other than current, and will
> > never get to cap_capset_check.
> > 
> > This brings the vmlinux size with my config down another
> > 16 bytes (making up for the 8 byte increase from the
> > last patch).
> > 
> > Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
> > ---
> >  security/commoncap.c |   22 +++-------------------
> >  1 files changed, 3 insertions(+), 19 deletions(-)
> > 
> > diff --git a/security/commoncap.c b/security/commoncap.c
> > index d48fdd8..e5afb7c 100644
> > --- a/security/commoncap.c
> > +++ b/security/commoncap.c
> > @@ -93,15 +93,6 @@ int cap_capget (struct task_struct *target, kernel_cap_t *effective,
> >  	return 0;
> >  }
> >  
> > -static inline int cap_block_setpcap(struct task_struct *target)
> > -{
> > -	/*
> > -	 * No support for remote process capability manipulation with
> > -	 * filesystem capability support.
> > -	 */
> > -	return (target != current);
> > -}
> > -
> >  static inline int cap_inh_is_capped(void)
> >  {
> >  	/*
> > @@ -112,14 +103,9 @@ static inline int cap_inh_is_capped(void)
> >  	return (cap_capable(current, CAP_SETPCAP) != 0);
> >  }
> >  
> > -static inline int cap_limit_ptraced_target(void) { return 1; }
> > -
> >  int cap_capset_check (struct task_struct *target, kernel_cap_t *effective,
> >  		      kernel_cap_t *inheritable, kernel_cap_t *permitted)
> >  {
> > -	if (cap_block_setpcap(target)) {
> > -		return -EPERM;
> > -	}
> >  	if (cap_inh_is_capped()
> >  	    && !cap_issubset(*inheritable,
> >  			     cap_combine(target->cap_inheritable,
> > @@ -343,11 +329,9 @@ void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
> >  				bprm->e_uid = current->uid;
> >  				bprm->e_gid = current->gid;
> >  			}
> > -			if (cap_limit_ptraced_target()) {
> > -				bprm->cap_post_exec_permitted = cap_intersect(
> > -					bprm->cap_post_exec_permitted,
> > -					current->cap_permitted);
> > -			}
> > +			bprm->cap_post_exec_permitted = cap_intersect(
> > +				bprm->cap_post_exec_permitted,
> > +				current->cap_permitted);
> >  		}
> >  	}
> >  
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