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

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Date:	Fri, 26 Sep 2008 21:39:17 -0700
From:	"Andrew G. Morgan" <morgan@...nel.org>
To:	"Serge E. Hallyn" <serue@...ibm.com>
CC:	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [PATCH 5/6] file capabilities: remove needless inline functions

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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
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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