On Wed, Jan 9, 2019 at 3:33 PM Stephen Smalley <sds@xxxxxxxxxxxxx> wrote:
> On 1/9/19 4:10 AM, Ondrej Mosnacek wrote:
> > This patch introduces a new security hook that is intended for
> > initializing the security data for newly created pseudo filesystem
> > objects (such as kernfs nodes) that provide a way of storing a
> > non-default security context, but need to operate independently from
> > mounts.
> >
> > The main motivation is to allow kernfs nodes to inherit the context of
> > the parent under SELinux, similar to the behavior of
> > security_inode_init_security(). Other LSMs may implement their own logic
> > for handling the creation of new nodes.
> >
> > Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
> > ---
> > include/linux/lsm_hooks.h | 5 +++++
> > include/linux/security.h | 12 ++++++++++++
> > security/security.c | 8 ++++++++
> > 3 files changed, 25 insertions(+)
> >
> > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> > index aaeb7fa24dc4..f2b4c0bf4a7b 100644
> > --- a/include/linux/lsm_hooks.h
> > +++ b/include/linux/lsm_hooks.h
> > @@ -1556,6 +1556,10 @@ union security_list_options {
> > int (*inode_copy_up)(struct dentry *src, struct cred **new);
> > int (*inode_copy_up_xattr)(const char *name);
> >
> > + int (*object_init_security)(void *parent_ctx, u32 parent_ctxlen,
> > + const struct qstr *qstr, u16 mode,
> > + void **ctx, u32 *ctxlen);
>
> You'll want to add a kerneldoc comment for the new hook; see the
> existing ones for the other hooks at the top of lsm_hooks.h.
Good point, will add that in v2, thanks.
>
> > +
> > int (*file_permission)(struct file *file, int mask);
> > int (*file_alloc_security)(struct file *file);
> > void (*file_free_security)(struct file *file);
> > @@ -1855,6 +1859,7 @@ struct security_hook_heads {
> > struct hlist_head inode_getsecid;
> > struct hlist_head inode_copy_up;
> > struct hlist_head inode_copy_up_xattr;
> > + struct hlist_head object_init_security;
> > struct hlist_head file_permission;
> > struct hlist_head file_alloc_security;
> > struct hlist_head file_free_security;
> > diff --git a/include/linux/security.h b/include/linux/security.h
> > index d170a5b031f3..e20d1f378ea4 100644
> > --- a/include/linux/security.h
> > +++ b/include/linux/security.h
> > @@ -315,6 +315,9 @@ int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer
> > void security_inode_getsecid(struct inode *inode, u32 *secid);
> > int security_inode_copy_up(struct dentry *src, struct cred **new);
> > int security_inode_copy_up_xattr(const char *name);
> > +int security_object_init_security(void *parent_ctx, u32 parent_ctxlen,
> > + const struct qstr *qstr, u16 mode,
> > + void **ctx, u32 *ctxlen);
> > int security_file_permission(struct file *file, int mask);
> > int security_file_alloc(struct file *file);
> > void security_file_free(struct file *file);
> > @@ -815,6 +818,15 @@ static inline int security_inode_copy_up_xattr(const char *name)
> > return -EOPNOTSUPP;
> > }
> >
> > +static inline int security_object_init_security(void *parent_ctx,
> > + u32 parent_ctxlen,
> > + const struct qstr *qstr,
> > + u16 mode, void **ctx,
> > + u32 *ctxlen)
> > +{
> > + return 0;
I just realized I will need to assign *ctx to NULL and *ctxlen to 0
here, since I chose to return 0 by default...
> > +}
> > +
> > static inline int security_file_permission(struct file *file, int mask)
> > {
> > return 0;
> > diff --git a/security/security.c b/security/security.c
> > index 04d173eb93f6..56e77368b87f 100644
> > --- a/security/security.c
> > +++ b/security/security.c
> > @@ -879,6 +879,14 @@ int security_inode_copy_up_xattr(const char *name)
> > }
> > EXPORT_SYMBOL(security_inode_copy_up_xattr);
> >
> > +int security_object_init_security(void *parent_ctx, u32 parent_ctxlen,
> > + const struct qstr *qstr, u16 mode,
> > + void **ctx, u32 *ctxlen)
> > +{
> > + return call_int_hook(object_init_security, 0, parent_ctx, parent_ctxlen,
> > + qstr, mode, ctx, ctxlen);
Same here, in case there is no object_init_security hook provided by the LSM.
> > +}
> > +
> > int security_file_permission(struct file *file, int mask)
> > {
> > int ret;
> >
>
--
Ondrej Mosnacek <omosnace at redhat dot com>
Associate Software Engineer, Security Technologies
Red Hat, Inc.
