Re: [PATCH v25 17/25] LSM: Use lsmcontext in security_inode_getsecctx

[Chuck Lever III <chuck.lever@oracle.com>]

Hi Casey-

> On Mar 9, 2021, at 9:42 AM, Casey Schaufler <casey@schaufler-ca.com> 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.
> 
> Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
> Acked-by: Paul Moore <paul@paul-moore.com>
> Reviewed-by: John Johansen <john.johansen@canonical.com>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> Cc: linux-nfs@vger.kernel.org

For the NFSD hunks in 15/25 and 17/25:

Acked-by: Chuck Lever <chuck.lever@oracle.com>


> ---
> 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 afccc4f257d0..a796268ec757 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2727,11 +2727,11 @@ 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;
> 
> @@ -2741,13 +2741,13 @@ 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
> 
> @@ -2844,9 +2844,7 @@ 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;
> @@ -2904,7 +2902,7 @@ 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);
> @@ -3324,8 +3322,7 @@ 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;
> 	}
> @@ -3346,10 +3343,8 @@ 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 d0e1b6ba330d..9dcc910036f4 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -582,7 +582,7 @@ 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 */
> 
> @@ -1442,7 +1442,8 @@ 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 73fb5c6c4cf8..b88f916e0698 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2337,9 +2337,18 @@ 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);
> 
> -- 
> 2.29.2
> 

--
Chuck Lever