On 11/13/19 10:19 AM, Casey Schaufler wrote:
> Change the security_dentry_init_security() interface to
> fill an lsmcontext structure instead of a void * data area
> and a length. The lone caller of this interface is NFS4,
> which may make copies of the data using its own mechanisms.
> A rework of the nfs4 code to use the lsmcontext properly
> is a significant project, so the coward's way out is taken,
> and the lsmcontext data from security_dentry_init_security()
> is copied, then released directly.
>
> This interface does not use the "display". There is currently
> not case where that is useful or reasonable.
>
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Reviewed-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Acked-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
> ---
> fs/nfs/nfs4proc.c | 26 ++++++++++++++++----------
> include/linux/security.h | 7 +++----
> security/security.c | 29 +++++++++++++++++++++++++----
> 3 files changed, 44 insertions(+), 18 deletions(-)
>
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index 74e9f4b7cc07..2f76741ee528 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -113,6 +113,7 @@ static inline struct nfs4_label *
> nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
> struct iattr *sattr, struct nfs4_label *label)
> {
> + struct lsmcontext context;
> int err;
>
> if (label == NULL)
> @@ -122,21 +123,26 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
> return NULL;
>
> err = security_dentry_init_security(dentry, sattr->ia_mode,
> - &dentry->d_name, (void **)&label->label, &label->len);
> - if (err == 0)
> - return label;
> + &dentry->d_name, &context);
> +
> + if (err)
> + return NULL;
> +
> + label->label = kmemdup(context.context, context.len, GFP_KERNEL);
> + if (label->label == NULL)
> + label = NULL;
> + else
> + label->len = context.len;
> +
> + security_release_secctx(&context);
> +
> + return label;
>
> - return NULL;
> }
> static inline void
> nfs4_label_release_security(struct nfs4_label *label)
> {
> - struct lsmcontext scaff; /* scaffolding */
> -
> - if (label) {
> - lsmcontext_init(&scaff, label->label, label->len, 0);
> - security_release_secctx(&scaff);
> - }
> + kfree(label->label);
> }
> static inline u32 *nfs4_bitmask(struct nfs_server *server, struct nfs4_label *label)
> {
> diff --git a/include/linux/security.h b/include/linux/security.h
> index e47cef3d62f0..3e333104720d 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -396,8 +396,8 @@ int security_add_mnt_opt(const char *option, const char *val,
> int len, void **mnt_opts);
> int security_move_mount(const struct path *from_path, const struct path *to_path);
> int security_dentry_init_security(struct dentry *dentry, int mode,
> - const struct qstr *name, void **ctx,
> - u32 *ctxlen);
> + const struct qstr *name,
> + struct lsmcontext *ctx);
> int security_dentry_create_files_as(struct dentry *dentry, int mode,
> struct qstr *name,
> const struct cred *old,
> @@ -788,8 +788,7 @@ static inline void security_inode_free(struct inode *inode)
> static inline int security_dentry_init_security(struct dentry *dentry,
> int mode,
> const struct qstr *name,
> - void **ctx,
> - u32 *ctxlen)
> + struct lsmcontext *ctx)
> {
> return -EOPNOTSUPP;
> }
> diff --git a/security/security.c b/security/security.c
> index 618d4f90936b..6f43dafe1249 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1011,12 +1011,33 @@ void security_inode_free(struct inode *inode)
> inode_free_by_rcu);
> }
>
> +/*
> + * security_dentry_init_security - initial context for a dentry
> + * @dentry: directory entry
> + * @mode: access mode
> + * @name: path name
> + * @context: resulting security context
> + *
> + * Use at most one security module to get the initial
> + * security context. Do not use the "display".
> + *
> + * Returns -EOPNOTSUPP if not supplied by any module or the module result.
> + */
> int security_dentry_init_security(struct dentry *dentry, int mode,
> - const struct qstr *name, void **ctx,
> - u32 *ctxlen)
> + const struct qstr *name,
> + struct lsmcontext *cp)
> {
> - return call_int_hook(dentry_init_security, -EOPNOTSUPP, dentry, mode,
> - name, ctx, ctxlen);
> + struct security_hook_list *hp;
> +
> + hlist_for_each_entry(hp, &security_hook_heads.dentry_init_security,
> + list) {
> + cp->slot = hp->lsmid->slot;
> + return hp->hook.dentry_init_security(dentry, mode, name,
> + (void **)&cp->context,
> + &cp->len);
> + }
> +
> + return -EOPNOTSUPP;
> }
> EXPORT_SYMBOL(security_dentry_init_security);
>
>
