Messages in this thread | | | Date | Tue, 7 Mar 2023 12:51:57 +0100 | Subject | Re: [PATCH v6 04/11] LSM: syscalls for current process attributes | From | Mickaël Salaün <> |
| |
On 22/02/2023 21:08, Casey Schaufler wrote: > Create a system call lsm_get_self_attr() to provide the security > module maintained attributes of the current process. > Create a system call lsm_set_self_attr() to set a security > module maintained attribute of the current process. > Historically these attributes have been exposed to user space via > entries in procfs under /proc/self/attr. > > The attribute value is provided in a lsm_ctx structure. The structure > identifys the size of the attribute, and the attribute value. The format > of the attribute value is defined by the security module. A flags field > is included for LSM specific information. It is currently unused and must > be 0. The total size of the data, including the lsm_ctx structure and any > padding, is maintained as well. > > struct lsm_ctx { > __u64 id; > __u64 flags; > __u64 len; > __u64 ctx_len; > __u8 ctx[]; > }; > > Two new LSM hooks are used to interface with the LSMs. > security_getselfattr() collects the lsm_ctx values from the > LSMs that support the hook, accounting for space requirements. > security_setselfattr() identifies which LSM the attribute is > intended for and passes it along. > > Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> > --- > Documentation/userspace-api/lsm.rst | 15 ++++ > include/linux/lsm_hook_defs.h | 4 ++ > include/linux/lsm_hooks.h | 9 +++ > include/linux/security.h | 19 +++++ > include/linux/syscalls.h | 4 ++ > include/uapi/linux/lsm.h | 33 +++++++++ > kernel/sys_ni.c | 4 ++ > security/Makefile | 1 + > security/lsm_syscalls.c | 104 ++++++++++++++++++++++++++++ > security/security.c | 82 ++++++++++++++++++++++ > 10 files changed, 275 insertions(+) > create mode 100644 security/lsm_syscalls.c >
[...]
> +/** > + * security_setselfattr - Set an LSM attribute on the current process. > + * @attr: which attribute to return > + * @ctx: the user-space source for the information > + * @size: the size of the data > + * > + * Set an LSM attribute for the current process. The LSM, attribute > + * and new value are included in @ctx. > + * > + * Returns 0 on seccess, an LSM specific value on failure. > + */ > +int security_setselfattr(u64 __user attr, struct lsm_ctx __user *ctx, > + size_t __user size) > +{ > + struct security_hook_list *hp; > + struct lsm_ctx lctx; > + > + if (size < sizeof(*ctx))
If the lsm_ctx struct could grow in the future, we should check the size of the struct to the last field for compatibility reasons, see Landlock's copy_min_struct_from_user().
> + return -EINVAL; > + if (copy_from_user(&lctx, ctx, sizeof(*ctx))) > + return -EFAULT; > + > + hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list) > + if ((hp->lsmid->id) == lctx.id) > + return hp->hook.setselfattr(attr, ctx, size); > + > + return LSM_RET_DEFAULT(setselfattr); > +} > + > int security_getprocattr(struct task_struct *p, int lsmid, const char *name, > char **value) > {
| |