Re: [PATCH v12 17/25] LSM: Use lsmcontext in security_inode_getsecctx

[Stephen Smalley <sds@xxxxxxxxxxxxx>]

On 12/16/19 5:36 PM, Casey Schaufler wrote:
> Change the security_inode_getsecctx() interface to fill
> a lsmcontext structure instead of data and length pointers.
> This provides the information about which LSM created the
> context so that security_release_secctx() can use the
> correct hook.
>
> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>

Acked-by: Stephen Smalley <sds@xxxxxxxxxxxxx>

> ---
>   fs/nfsd/nfs4xdr.c        | 23 +++++++++--------------
>   include/linux/security.h |  5 +++--
>   security/security.c      | 13 +++++++++++--
>   3 files changed, 23 insertions(+), 18 deletions(-)
>
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index e20011281915..98d20178e60f 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2304,11 +2304,11 @@ nfsd4_encode_layout_types(struct xdr_stream *xdr, u32 layout_types)
>   #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
>   static inline __be32
>   nfsd4_encode_security_label(struct xdr_stream *xdr, struct svc_rqst *rqstp,
> -			    void *context, int len)
> +			    struct lsmcontext *context)
>   {
>   	__be32 *p;
>   
> -	p = xdr_reserve_space(xdr, len + 4 + 4 + 4);
> +	p = xdr_reserve_space(xdr, context->len + 4 + 4 + 4);
>   	if (!p)
>   		return nfserr_resource;
>   
> @@ -2318,13 +2318,13 @@ nfsd4_encode_security_label(struct xdr_stream *xdr, struct svc_rqst *rqstp,
>   	 */
>   	*p++ = cpu_to_be32(0); /* lfs */
>   	*p++ = cpu_to_be32(0); /* pi */
> -	p = xdr_encode_opaque(p, context, len);
> +	p = xdr_encode_opaque(p, context->context, context->len);
>   	return 0;
>   }
>   #else
>   static inline __be32
>   nfsd4_encode_security_label(struct xdr_stream *xdr, struct svc_rqst *rqstp,
> -			    void *context, int len)
> +			    struct lsmcontext *context)
>   { return 0; }
>   #endif
>   
> @@ -2421,9 +2421,7 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
>   	int err;
>   	struct nfs4_acl *acl = NULL;
>   #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
> -	struct lsmcontext scaff; /* scaffolding */
> -	void *context = NULL;
> -	int contextlen;
> +	struct lsmcontext context = { };
>   #endif
>   	bool contextsupport = false;
>   	struct nfsd4_compoundres *resp = rqstp->rq_resp;
> @@ -2481,7 +2479,7 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
>   	     bmval0 & FATTR4_WORD0_SUPPORTED_ATTRS) {
>   		if (exp->ex_flags & NFSEXP_SECURITY_LABEL)
>   			err = security_inode_getsecctx(d_inode(dentry),
> -						&context, &contextlen);
> +						       &context);
>   		else
>   			err = -EOPNOTSUPP;
>   		contextsupport = (err == 0);
> @@ -2911,8 +2909,7 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
>   
>   #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
>   	if (bmval2 & FATTR4_WORD2_SECURITY_LABEL) {
> -		status = nfsd4_encode_security_label(xdr, rqstp, context,
> -								contextlen);
> +		status = nfsd4_encode_security_label(xdr, rqstp, &context);
>   		if (status)
>   			goto out;
>   	}
> @@ -2924,10 +2921,8 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
>   
>   out:
>   #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
> -	if (context) {
> -		lsmcontext_init(&scaff, context, contextlen, 0); /*scaffolding*/
> -		security_release_secctx(&scaff);
> -	}
> +	if (context.context)
> +		security_release_secctx(&context);
>   #endif /* CONFIG_NFSD_V4_SECURITY_LABEL */
>   	kfree(acl);
>   	if (tempfh) {
> diff --git a/include/linux/security.h b/include/linux/security.h
> index a5eba06a9382..d0fab9f5dddf 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -537,7 +537,7 @@ void security_release_secctx(struct lsmcontext *cp);
>   void security_inode_invalidate_secctx(struct inode *inode);
>   int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
>   int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
> -int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
> +int security_inode_getsecctx(struct inode *inode, struct lsmcontext *cp);
>   int security_locked_down(enum lockdown_reason what);
>   #else /* CONFIG_SECURITY */
>   
> @@ -1362,7 +1362,8 @@ static inline int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32
>   {
>   	return -EOPNOTSUPP;
>   }
> -static inline int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
> +static inline int security_inode_getsecctx(struct inode *inode,
> +					   struct lsmcontext *cp)
>   {
>   	return -EOPNOTSUPP;
>   }
> diff --git a/security/security.c b/security/security.c
> index 8aa107b57af9..963641acf9dc 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2207,9 +2207,18 @@ int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen)
>   }
>   EXPORT_SYMBOL(security_inode_setsecctx);
>   
> -int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
> +int security_inode_getsecctx(struct inode *inode, struct lsmcontext *cp)
>   {
> -	return call_int_hook(inode_getsecctx, -EOPNOTSUPP, inode, ctx, ctxlen);
> +	struct security_hook_list *hp;
> +
> +	memset(cp, 0, sizeof(*cp));
> +
> +	hlist_for_each_entry(hp, &security_hook_heads.inode_getsecctx, list) {
> +		cp->slot = hp->lsmid->slot;
> +		return hp->hook.inode_getsecctx(inode, (void **)&cp->context,
> +						&cp->len);
> +	}
> +	return -EOPNOTSUPP;
>   }
>   EXPORT_SYMBOL(security_inode_getsecctx);
>