[PATCH v4 19/23] LSM: Use lsmcontext in security_inode_getsecctx
Kees Cook
keescook at chromium.org
Wed Jun 26 23:16:02 UTC 2019
On Wed, Jun 26, 2019 at 12:22:30PM -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. A lsmcontext is used within kernfs to store
> the security information as well.
>
> Signed-off-by: Casey Schaufler <casey at schaufler-ca.com>
Reviewed-by: Kees Cook <keescook at chromium.org>
-Kees
> ---
> fs/kernfs/dir.c | 8 ++------
> fs/kernfs/inode.c | 34 ++++++++++++----------------------
> fs/kernfs/kernfs-internal.h | 3 +--
> fs/nfsd/nfs4xdr.c | 23 +++++++++--------------
> include/linux/security.h | 5 +++--
> security/security.c | 14 ++++++++++++--
> 6 files changed, 39 insertions(+), 48 deletions(-)
>
> diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
> index 92afad387237..1d000289d8b7 100644
> --- a/fs/kernfs/dir.c
> +++ b/fs/kernfs/dir.c
> @@ -532,12 +532,8 @@ void kernfs_put(struct kernfs_node *kn)
> kfree_const(kn->name);
>
> if (kn->iattr) {
> - struct lsmcontext scaff; /* scaffolding */
> - if (kn->iattr->ia_secdata) {
> - lsmcontext_init(&scaff, kn->iattr->ia_secdata,
> - kn->iattr->ia_secdata_len, 0);
> - security_release_secctx(&scaff);
> - }
> + if (kn->iattr->ia_context.context)
> + security_release_secctx(&kn->iattr->ia_context);
> simple_xattrs_free(&kn->iattr->xattrs);
> kmem_cache_free(kernfs_iattrs_cache, kn->iattr);
> }
> diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
> index 02cde9dac5ee..ffbf7863306d 100644
> --- a/fs/kernfs/inode.c
> +++ b/fs/kernfs/inode.c
> @@ -135,21 +135,14 @@ int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
> return error;
> }
>
> -static int kernfs_node_setsecdata(struct kernfs_iattrs *attrs, void **secdata,
> - u32 *secdata_len)
> +static void kernfs_node_setsecdata(struct kernfs_iattrs *attrs,
> + struct lsmcontext *cp)
> {
> - void *old_secdata;
> - size_t old_secdata_len;
> + struct lsmcontext old_context;
>
> - old_secdata = attrs->ia_secdata;
> - old_secdata_len = attrs->ia_secdata_len;
> -
> - attrs->ia_secdata = *secdata;
> - attrs->ia_secdata_len = *secdata_len;
> -
> - *secdata = old_secdata;
> - *secdata_len = old_secdata_len;
> - return 0;
> + old_context = attrs->ia_context;
> + attrs->ia_context = *cp;
> + *cp = old_context;
> }
>
> ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
> @@ -192,8 +185,8 @@ static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
> * persistent copy in kernfs_node.
> */
> set_inode_attr(inode, &attrs->ia_iattr);
> - security_inode_notifysecctx(inode, attrs->ia_secdata,
> - attrs->ia_secdata_len);
> + security_inode_notifysecctx(inode, attrs->ia_context.context,
> + attrs->ia_context.len);
> }
>
> if (kernfs_type(kn) == KERNFS_DIR)
> @@ -350,8 +343,6 @@ static int kernfs_security_xattr_set(const struct xattr_handler *handler,
> struct kernfs_node *kn = inode->i_private;
> struct kernfs_iattrs *attrs;
> struct lsmcontext context;
> - void *secdata;
> - u32 secdata_len = 0;
> int error;
>
> attrs = kernfs_iattrs(kn);
> @@ -361,18 +352,17 @@ static int kernfs_security_xattr_set(const struct xattr_handler *handler,
> error = security_inode_setsecurity(inode, suffix, value, size, flags);
> if (error)
> return error;
> - error = security_inode_getsecctx(inode, &secdata, &secdata_len);
> + error = security_inode_getsecctx(inode, &context);
> if (error)
> return error;
>
> mutex_lock(&kernfs_mutex);
> - error = kernfs_node_setsecdata(attrs, &secdata, &secdata_len);
> + kernfs_node_setsecdata(attrs, &context);
> mutex_unlock(&kernfs_mutex);
>
> - if (secdata) {
> - lsmcontext_init(&context, secdata, secdata_len, 0);
> + if (context.context)
> security_release_secctx(&context);
> - }
> +
> return error;
> }
>
> diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
> index 0b7d197a904c..844a028d282f 100644
> --- a/fs/kernfs/kernfs-internal.h
> +++ b/fs/kernfs/kernfs-internal.h
> @@ -21,8 +21,7 @@
>
> struct kernfs_iattrs {
> struct iattr ia_iattr;
> - void *ia_secdata;
> - u32 ia_secdata_len;
> + struct lsmcontext ia_context;
>
> struct simple_xattrs xattrs;
> };
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index bb3db033e144..1209083565dd 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
>
> @@ -2420,9 +2420,7 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
> __be32 status;
> int err;
> struct nfs4_acl *acl = NULL;
> - struct lsmcontext scaff; /* scaffolding */
> - void *context = NULL;
> - int contextlen;
> + struct lsmcontext context;
> bool contextsupport = false;
> struct nfsd4_compoundres *resp = rqstp->rq_resp;
> u32 minorversion = resp->cstate.minorversion;
> @@ -2479,7 +2477,7 @@ 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);
> @@ -2908,8 +2906,7 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
> }
>
> 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;
> }
> @@ -2920,10 +2917,8 @@ 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 2674eb70c2d7..c16aea55be97 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -489,7 +489,7 @@ 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);
> #else /* CONFIG_SECURITY */
>
> static inline int call_lsm_notifier(enum lsm_event event, void *data)
> @@ -1290,7 +1290,8 @@ 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 61cdc6bcd32e..45b9f905f5c0 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2164,9 +2164,19 @@ 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);
> + int *display = current->security;
> + struct security_hook_list *hp;
> +
> + hlist_for_each_entry(hp, &security_hook_heads.inode_getsecctx, list)
> + if (*display == LSMBLOB_INVALID ||
> + *display == hp->lsmid->slot) {
> + cp->slot = hp->lsmid->slot;
> + return hp->hook.inode_getsecctx(inode,
> + (void **)&cp->context, &cp->len);
> + }
> + return -EOPNOTSUPP;
> }
> EXPORT_SYMBOL(security_inode_getsecctx);
>
> --
> 2.20.1
>
--
Kees Cook
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