Re: [Patch 1/2] selinux: ajust rules for ATTR_FORCE

[Amerigo Wang <amwang@redhat.com>]

OGAWA Hirofumi wrote:
> Could you review this? I've added ATTR_TIMES_SET to check explicit
> utimes(), and tried it with minimum change.
>
> [I'm not sure this handles notify_change() usage of nfsd (and perhaps
> other network fs too) correctly, and whether selinux may want to check
> it. I guess network fs _may_ try to change the multiple attributes at a
> time. Well, even if it's true, it would be another topic...]
>
>   

Ah, according to the discussion here, I know I misunderstood 
ATTR_FORCE... sorry.
> OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
>
>
> From: Amerigo Wang <amwang@redhat.com>
>
> As suggested by OGAWA Hirofumi in thread: http://lkml.org/lkml/2009/8/7/132,
> we should let selinux_inode_setattr() to match our ATTR_* rules.
> ATTR_FORCE should not force things like ATTR_SIZE.
>
> Cc: Stephen Smalley <sds@tycho.nsa.gov>
> Cc: Eric Paris <eparis@redhat.com>
> Signed-off-by: WANG Cong <amwang@redhat.com>
> [tweaks]
> Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
>   

Great!

Some comments below.

> ---
>
>  security/selinux/hooks.c |   13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff -puN security/selinux/hooks.c~selinux-truncate-fix security/selinux/hooks.c
> --- linux-2.6/security/selinux/hooks.c~selinux-truncate-fix	2009-08-18 03:50:09.000000000 +0900
> +++ linux-2.6-hirofumi/security/selinux/hooks.c	2009-08-18 05:35:11.000000000 +0900
> @@ -2711,12 +2711,17 @@ static int selinux_inode_permission(stru
>  static int selinux_inode_setattr(struct dentry *dentry, struct iattr *iattr)
>  {
>  	const struct cred *cred = current_cred();
> +	unsigned int ia_valid = iattr->ia_valid;
>  
> -	if (iattr->ia_valid & ATTR_FORCE)
> -		return 0;
> +	/* ATTR_FORCE is just used for ATTR_KILL_S[UG]ID. */
> +	if (ia_valid & ATTR_FORCE) {
> +		ia_valid &= ~(ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_MODE);
> +		if (!ia_valid)
> +			return 0;
>   

So if I read this correctly, (ATTR_FORCE| ATTR_KILL_SUID|ATTR_MODE) will 
not return here, since 'ia_valid' will be ATTR_FORCE finally.

I think you forgot to clear ATTR_FORCE here...

> +	}
>  
> -	if (iattr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID |
> -			       ATTR_ATIME_SET | ATTR_MTIME_SET))
> +	if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID |
> +			ATTR_ATIME_SET | ATTR_MTIME_SET | ATTR_TIMES_SET))
>  		return dentry_has_perm(cred, NULL, dentry, FILE__SETATTR);
>  
>  	return dentry_has_perm(cred, NULL, dentry, FILE__WRITE);
> _
>
>   
I am not sure about ATTR_TIMES_SET here, but looks fine. :-/