On Mon, Apr 06, 2020 at 05:01:52PM -0700, 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.
>
> Acked-by: Stephen Smalley <sds@xxxxxxxxxxxxx>
> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
-Kees
> ---
> 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 df308b1b37fa..ac8eb77d0053 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2379,11 +2379,11 @@ 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;
>
> @@ -2393,13 +2393,13 @@ 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
>
> @@ -2496,9 +2496,7 @@ 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;
> @@ -2556,7 +2554,7 @@ 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);
> @@ -2986,8 +2984,7 @@ 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;
> }
> @@ -2999,10 +2996,8 @@ 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 ec64ccd2e168..fac5547dd89e 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -556,7 +556,7 @@ 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 */
>
> @@ -1382,7 +1382,8 @@ 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 356c5cd94c48..84f33bd4990a 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2211,9 +2211,18 @@ 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);
>
> --
> 2.24.1
>
--
Kees Cook
