linux-kernel - Re: [TOMOYO #9 (2.6.27-rc7-mm1) 1/6] LSM adapter functions.

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Date:	Thu, 25 Sep 2008 11:59:54 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Kentaro Takeda <takedakn@...data.co.jp>
Cc:	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, haradats@...data.co.jp,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Subject: Re: [TOMOYO #9 (2.6.27-rc7-mm1) 1/6] LSM adapter functions.

Quoting Kentaro Takeda (takedakn@...data.co.jp):
> Signed-off-by: Kentaro Takeda <takedakn@...data.co.jp>
> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Signed-off-by: Toshiharu Harada <haradats@...data.co.jp>

So IMO there is some major badness here in the form of copying all of
those functions out of fs/namei.c.  I think we need to discuss
case-by-case whether using the functions is appropriate (and hence
they should be made non-static in fs/namei.c), or whether the intended
goal should be met some other way.  For instance:
 
> ---
>  security/tomoyo/tomoyo.c |  341 +++++++++++++++++++++++++++++++++++++++++++++++
>  security/tomoyo/tomoyo.h |   97 +++++++++++++
>  2 files changed, 438 insertions(+)
> 

...

> +static int tmy_path_mknod(struct path *parent, struct dentry *dentry, int mode,
> +			  unsigned int dev)
> +{
> +	struct vfsmount *mnt = parent->mnt;
> +	struct inode *dir = parent->dentry->d_inode;
> +	int error = 0;
> +
> +	switch (mode & S_IFMT) {
> +	case S_IFREG:
> +	case 0:
> +		error = may_create(dir, dentry);

Isn't may_create already done at the top of vfs_mknod() and vfs_create()?

> +		if (error)
> +			return error;
> +		if (!dir->i_op || !dir->i_op->create)
> +			return -EACCES; /* shouldn't it be ENOSYS? */
> +		break;
> +	case S_IFCHR:
> +	case S_IFBLK:
> +	case S_IFIFO:
> +	case S_IFSOCK:
> +		error = may_create(dir, dentry);

likewise...

> +		if (error)
> +			return error;
> +		if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
> +			return -EPERM;

likewise...

> +		if (!dir->i_op || !dir->i_op->mknod)
> +			return -EPERM;
> +		error = devcgroup_inode_mknod(mode, dev);

likewise...  (except in the case of fifo/sock, devcgroup should not be
consulted as I'm not sure it'll handle that properly - have you tested
tis with the device cgroup enabled?)

> +		if (error)
> +			return error;
> +		break;
> +	default:
> +		return 0;
> +	}
> +	switch (mode & S_IFMT) {
> +	case S_IFREG:
> +	case 0:
> +		error = tmy_check_1path_perm(TMY_TYPE_CREATE_ACL, dentry, mnt);
> +		break;
> +	case S_IFCHR:
> +		error = tmy_check_1path_perm(TMY_TYPE_MKCHAR_ACL, dentry, mnt);
> +		break;
> +	case S_IFBLK:
> +		error = tmy_check_1path_perm(TMY_TYPE_MKBLOCK_ACL, dentry, mnt);
> +		break;
> +	case S_IFIFO:
> +		error = tmy_check_1path_perm(TMY_TYPE_MKFIFO_ACL, dentry, mnt);
> +		break;
> +	case S_IFSOCK:
> +		error = tmy_check_1path_perm(TMY_TYPE_MKSOCK_ACL, dentry, mnt);
> +		break;
> +	}
> +	return error;
> +}

-serge
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