Re: [PATCH v4 4/7] selinux: Add accessor functions for inode->i_security

[Stephen Smalley <sds@xxxxxxxxxxxxx>]

On 10/28/2015 08:47 PM, Andreas Gruenbacher wrote:
> Add functions dentry_security and inode_security for accessing
> inode->i_security.  These functions initially don't do much, but they
> will later be used to revalidate the security labels when necessary.
>
> Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>

Acked-by: Stephen Smalley <sds@xxxxxxxxxxxxx>

> ---
>   security/selinux/hooks.c | 97 ++++++++++++++++++++++++++++--------------------
>   1 file changed, 56 insertions(+), 41 deletions(-)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index a8f09af..48d1908 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -241,6 +241,24 @@ static int inode_alloc_security(struct inode *inode)
>   	return 0;
>   }
>
> +/*
> + * Get the security label of an inode.
> + */
> +static struct inode_security_struct *inode_security(struct inode *inode)
> +{
> +	return inode->i_security;
> +}
> +
> +/*
> + * Get the security label of a dentry's backing inode.
> + */
> +static struct inode_security_struct *backing_inode_security(struct dentry *dentry)
> +{
> +	struct inode *inode = d_backing_inode(dentry);
> +
> +	return inode->i_security;
> +}
> +
>   static void inode_free_rcu(struct rcu_head *head)
>   {
>   	struct inode_security_struct *isec;
> @@ -564,8 +582,8 @@ static int selinux_get_mnt_opts(const struct super_block *sb,
>   		opts->mnt_opts_flags[i++] = DEFCONTEXT_MNT;
>   	}
>   	if (sbsec->flags & ROOTCONTEXT_MNT) {
> -		struct inode *root = d_backing_inode(sbsec->sb->s_root);
> -		struct inode_security_struct *isec = root->i_security;
> +		struct dentry *root = sbsec->sb->s_root;
> +		struct inode_security_struct *isec = backing_inode_security(root);
>
>   		rc = security_sid_to_context(isec->sid, &context, &len);
>   		if (rc)
> @@ -620,8 +638,8 @@ static int selinux_set_mnt_opts(struct super_block *sb,
>   	int rc = 0, i;
>   	struct superblock_security_struct *sbsec = sb->s_security;
>   	const char *name = sb->s_type->name;
> -	struct inode *inode = d_backing_inode(sbsec->sb->s_root);
> -	struct inode_security_struct *root_isec = inode->i_security;
> +	struct dentry *root = sbsec->sb->s_root;
> +	struct inode_security_struct *root_isec = backing_inode_security(root);
>   	u32 fscontext_sid = 0, context_sid = 0, rootcontext_sid = 0;
>   	u32 defcontext_sid = 0;
>   	char **mount_options = opts->mnt_opts;
> @@ -852,8 +870,8 @@ static int selinux_cmp_sb_context(const struct super_block *oldsb,
>   	if ((oldflags & DEFCONTEXT_MNT) && old->def_sid != new->def_sid)
>   		goto mismatch;
>   	if (oldflags & ROOTCONTEXT_MNT) {
> -		struct inode_security_struct *oldroot = d_backing_inode(oldsb->s_root)->i_security;
> -		struct inode_security_struct *newroot = d_backing_inode(newsb->s_root)->i_security;
> +		struct inode_security_struct *oldroot = backing_inode_security(oldsb->s_root);
> +		struct inode_security_struct *newroot = backing_inode_security(newsb->s_root);
>   		if (oldroot->sid != newroot->sid)
>   			goto mismatch;
>   	}
> @@ -903,17 +921,14 @@ static int selinux_sb_clone_mnt_opts(const struct super_block *oldsb,
>   		if (!set_fscontext)
>   			newsbsec->sid = sid;
>   		if (!set_rootcontext) {
> -			struct inode *newinode = d_backing_inode(newsb->s_root);
> -			struct inode_security_struct *newisec = newinode->i_security;
> +			struct inode_security_struct *newisec = backing_inode_security(newsb->s_root);
>   			newisec->sid = sid;
>   		}
>   		newsbsec->mntpoint_sid = sid;
>   	}
>   	if (set_rootcontext) {
> -		const struct inode *oldinode = d_backing_inode(oldsb->s_root);
> -		const struct inode_security_struct *oldisec = oldinode->i_security;
> -		struct inode *newinode = d_backing_inode(newsb->s_root);
> -		struct inode_security_struct *newisec = newinode->i_security;
> +		const struct inode_security_struct *oldisec = backing_inode_security(oldsb->s_root);
> +		struct inode_security_struct *newisec = backing_inode_security(newsb->s_root);
>
>   		newisec->sid = oldisec->sid;
>   	}
> @@ -1712,13 +1727,13 @@ out:
>   /*
>    * Determine the label for an inode that might be unioned.
>    */
> -static int selinux_determine_inode_label(const struct inode *dir,
> +static int selinux_determine_inode_label(struct inode *dir,
>   					 const struct qstr *name,
>   					 u16 tclass,
>   					 u32 *_new_isid)
>   {
>   	const struct superblock_security_struct *sbsec = dir->i_sb->s_security;
> -	const struct inode_security_struct *dsec = dir->i_security;
> +	const struct inode_security_struct *dsec = inode_security(dir);
>   	const struct task_security_struct *tsec = current_security();
>
>   	if ((sbsec->flags & SE_SBINITIALIZED) &&
> @@ -1747,7 +1762,7 @@ static int may_create(struct inode *dir,
>   	struct common_audit_data ad;
>   	int rc;
>
> -	dsec = dir->i_security;
> +	dsec = inode_security(dir);
>   	sbsec = dir->i_sb->s_security;
>
>   	sid = tsec->sid;
> @@ -1800,8 +1815,8 @@ static int may_link(struct inode *dir,
>   	u32 av;
>   	int rc;
>
> -	dsec = dir->i_security;
> -	isec = d_backing_inode(dentry)->i_security;
> +	dsec = inode_security(dir);
> +	isec = backing_inode_security(dentry);
>
>   	ad.type = LSM_AUDIT_DATA_DENTRY;
>   	ad.u.dentry = dentry;
> @@ -1844,10 +1859,10 @@ static inline int may_rename(struct inode *old_dir,
>   	int old_is_dir, new_is_dir;
>   	int rc;
>
> -	old_dsec = old_dir->i_security;
> -	old_isec = d_backing_inode(old_dentry)->i_security;
> +	old_dsec = inode_security(old_dir);
> +	old_isec = backing_inode_security(old_dentry);
>   	old_is_dir = d_is_dir(old_dentry);
> -	new_dsec = new_dir->i_security;
> +	new_dsec = inode_security(new_dir);
>
>   	ad.type = LSM_AUDIT_DATA_DENTRY;
>
> @@ -1875,7 +1890,7 @@ static inline int may_rename(struct inode *old_dir,
>   	if (rc)
>   		return rc;
>   	if (d_is_positive(new_dentry)) {
> -		new_isec = d_backing_inode(new_dentry)->i_security;
> +		new_isec = backing_inode_security(new_dentry);
>   		new_is_dir = d_is_dir(new_dentry);
>   		rc = avc_has_perm(sid, new_isec->sid,
>   				  new_isec->sclass,
> @@ -2011,8 +2026,8 @@ static int selinux_binder_transfer_file(struct task_struct *from,
>   {
>   	u32 sid = task_sid(to);
>   	struct file_security_struct *fsec = file->f_security;
> -	struct inode *inode = d_backing_inode(file->f_path.dentry);
> -	struct inode_security_struct *isec = inode->i_security;
> +	struct dentry *dentry = file->f_path.dentry;
> +	struct inode_security_struct *isec = backing_inode_security(dentry);
>   	struct common_audit_data ad;
>   	int rc;
>
> @@ -2028,7 +2043,7 @@ static int selinux_binder_transfer_file(struct task_struct *from,
>   			return rc;
>   	}
>
> -	if (unlikely(IS_PRIVATE(inode)))
> +	if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
>   		return 0;
>
>   	return avc_has_perm(sid, isec->sid, isec->sclass, file_to_av(file),
> @@ -2217,7 +2232,7 @@ static int selinux_bprm_set_creds(struct linux_binprm *bprm)
>
>   	old_tsec = current_security();
>   	new_tsec = bprm->cred->security;
> -	isec = inode->i_security;
> +	isec = inode_security(inode);
>
>   	/* Default to the current task SID. */
>   	new_tsec->sid = old_tsec->sid;
> @@ -2642,7 +2657,7 @@ static int selinux_sb_remount(struct super_block *sb, void *data)
>   			break;
>   		case ROOTCONTEXT_MNT: {
>   			struct inode_security_struct *root_isec;
> -			root_isec = d_backing_inode(sb->s_root)->i_security;
> +			root_isec = backing_inode_security(sb->s_root);
>
>   			if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid, sid))
>   				goto out_bad_option;
> @@ -2859,7 +2874,7 @@ static int selinux_inode_follow_link(struct dentry *dentry, struct inode *inode,
>   	ad.type = LSM_AUDIT_DATA_DENTRY;
>   	ad.u.dentry = dentry;
>   	sid = cred_sid(cred);
> -	isec = inode->i_security;
> +	isec = inode_security(inode);
>
>   	return avc_has_perm_flags(sid, isec->sid, isec->sclass, FILE__READ, &ad,
>   				  rcu ? MAY_NOT_BLOCK : 0);
> @@ -2911,7 +2926,7 @@ static int selinux_inode_permission(struct inode *inode, int mask)
>   	perms = file_mask_to_av(inode->i_mode, mask);
>
>   	sid = cred_sid(cred);
> -	isec = inode->i_security;
> +	isec = inode_security(inode);
>
>   	rc = avc_has_perm_noaudit(sid, isec->sid, isec->sclass, perms, 0, &avd);
>   	audited = avc_audit_required(perms, &avd, rc,
> @@ -2980,7 +2995,7 @@ static int selinux_inode_setxattr(struct dentry *dentry, const char *name,
>   				  const void *value, size_t size, int flags)
>   {
>   	struct inode *inode = d_backing_inode(dentry);
> -	struct inode_security_struct *isec = inode->i_security;
> +	struct inode_security_struct *isec = backing_inode_security(dentry);
>   	struct superblock_security_struct *sbsec;
>   	struct common_audit_data ad;
>   	u32 newsid, sid = current_sid();
> @@ -3057,7 +3072,7 @@ static void selinux_inode_post_setxattr(struct dentry *dentry, const char *name,
>   					int flags)
>   {
>   	struct inode *inode = d_backing_inode(dentry);
> -	struct inode_security_struct *isec = inode->i_security;
> +	struct inode_security_struct *isec = backing_inode_security(dentry);
>   	u32 newsid;
>   	int rc;
>
> @@ -3115,7 +3130,7 @@ static int selinux_inode_getsecurity(struct inode *inode, const char *name, void
>   	u32 size;
>   	int error;
>   	char *context = NULL;
> -	struct inode_security_struct *isec = inode->i_security;
> +	struct inode_security_struct *isec = inode_security(inode);
>
>   	if (strcmp(name, XATTR_SELINUX_SUFFIX))
>   		return -EOPNOTSUPP;
> @@ -3154,7 +3169,7 @@ out_nofree:
>   static int selinux_inode_setsecurity(struct inode *inode, const char *name,
>   				     const void *value, size_t size, int flags)
>   {
> -	struct inode_security_struct *isec = inode->i_security;
> +	struct inode_security_struct *isec = inode_security(inode);
>   	u32 newsid;
>   	int rc;
>
> @@ -3184,7 +3199,7 @@ static int selinux_inode_listsecurity(struct inode *inode, char *buffer, size_t
>
>   static void selinux_inode_getsecid(struct inode *inode, u32 *secid)
>   {
> -	struct inode_security_struct *isec = inode->i_security;
> +	struct inode_security_struct *isec = inode_security(inode);
>   	*secid = isec->sid;
>   }
>
> @@ -3207,7 +3222,7 @@ static int selinux_file_permission(struct file *file, int mask)
>   {
>   	struct inode *inode = file_inode(file);
>   	struct file_security_struct *fsec = file->f_security;
> -	struct inode_security_struct *isec = inode->i_security;
> +	struct inode_security_struct *isec = inode_security(inode);
>   	u32 sid = current_sid();
>
>   	if (!mask)
> @@ -3242,7 +3257,7 @@ int ioctl_has_perm(const struct cred *cred, struct file *file,
>   	struct common_audit_data ad;
>   	struct file_security_struct *fsec = file->f_security;
>   	struct inode *inode = file_inode(file);
> -	struct inode_security_struct *isec = inode->i_security;
> +	struct inode_security_struct *isec = inode_security(inode);
>   	struct lsm_ioctlop_audit ioctl;
>   	u32 ssid = cred_sid(cred);
>   	int rc;
> @@ -3506,7 +3521,7 @@ static int selinux_file_open(struct file *file, const struct cred *cred)
>   	struct inode_security_struct *isec;
>
>   	fsec = file->f_security;
> -	isec = file_inode(file)->i_security;
> +	isec = inode_security(file_inode(file));
>   	/*
>   	 * Save inode label and policy sequence number
>   	 * at open-time so that selinux_file_permission
> @@ -3624,7 +3639,7 @@ static int selinux_kernel_act_as(struct cred *new, u32 secid)
>    */
>   static int selinux_kernel_create_files_as(struct cred *new, struct inode *inode)
>   {
> -	struct inode_security_struct *isec = inode->i_security;
> +	struct inode_security_struct *isec = inode_security(inode);
>   	struct task_security_struct *tsec = new->security;
>   	u32 sid = current_sid();
>   	int ret;
> @@ -4065,7 +4080,7 @@ static int selinux_socket_post_create(struct socket *sock, int family,
>   				      int type, int protocol, int kern)
>   {
>   	const struct task_security_struct *tsec = current_security();
> -	struct inode_security_struct *isec = SOCK_INODE(sock)->i_security;
> +	struct inode_security_struct *isec = inode_security(SOCK_INODE(sock));
>   	struct sk_security_struct *sksec;
>   	int err = 0;
>
> @@ -4265,9 +4280,9 @@ static int selinux_socket_accept(struct socket *sock, struct socket *newsock)
>   	if (err)
>   		return err;
>
> -	newisec = SOCK_INODE(newsock)->i_security;
> +	newisec = inode_security(SOCK_INODE(newsock));
>
> -	isec = SOCK_INODE(sock)->i_security;
> +	isec = inode_security(SOCK_INODE(sock));
>   	newisec->sclass = isec->sclass;
>   	newisec->sid = isec->sid;
>   	newisec->initialized = 1;
> @@ -4605,7 +4620,7 @@ static void selinux_sk_getsecid(struct sock *sk, u32 *secid)
>
>   static void selinux_sock_graft(struct sock *sk, struct socket *parent)
>   {
> -	struct inode_security_struct *isec = SOCK_INODE(parent)->i_security;
> +	struct inode_security_struct *isec = inode_security(SOCK_INODE(parent));
>   	struct sk_security_struct *sksec = sk->sk_security;
>
>   	if (sk->sk_family == PF_INET || sk->sk_family == PF_INET6 ||

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