On Wed, Mar 15, 2023 at 6:50 PM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote:
>
> Add lsm_name_to_attr(), which translates a text string to a
> LSM_ATTR value if one is available.
>
> Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
> the trailing attribute value.
>
> All are used in module specific components of LSM system calls.
>
> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
> ---
> include/linux/security.h | 13 ++++++++++
> security/lsm_syscalls.c | 51 ++++++++++++++++++++++++++++++++++++++++
> security/security.c | 31 ++++++++++++++++++++++++
> 3 files changed, 95 insertions(+)
...
> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
> index 6efbe244d304..55d849ad5d6e 100644
> --- a/security/lsm_syscalls.c
> +++ b/security/lsm_syscalls.c
> @@ -17,6 +17,57 @@
> #include <linux/lsm_hooks.h>
> #include <uapi/linux/lsm.h>
>
> +struct attr_map {
> + char *name;
> + u64 attr;
> +};
> +
> +static const struct attr_map lsm_attr_names[] = {
> + {
> + .name = "current",
> + .attr = LSM_ATTR_CURRENT,
> + },
> + {
> + .name = "exec",
> + .attr = LSM_ATTR_EXEC,
> + },
> + {
> + .name = "fscreate",
> + .attr = LSM_ATTR_FSCREATE,
> + },
> + {
> + .name = "keycreate",
> + .attr = LSM_ATTR_KEYCREATE,
> + },
> + {
> + .name = "prev",
> + .attr = LSM_ATTR_PREV,
> + },
> + {
> + .name = "sockcreate",
> + .attr = LSM_ATTR_SOCKCREATE,
> + },
> +};
> +
> +/**
> + * lsm_name_to_attr - map an LSM attribute name to its ID
> + * @name: name of the attribute
> + *
> + * Look the given @name up in the table of know attribute names.
> + *
> + * Returns the LSM attribute value associated with @name, or 0 if
> + * there is no mapping.
> + */
> +u64 lsm_name_to_attr(const char *name)
> +{
> + int i;
> +
> + for (i = 0; i < ARRAY_SIZE(lsm_attr_names); i++)
> + if (!strcmp(name, lsm_attr_names[i].name))
> + return lsm_attr_names[i].attr;
I'm pretty sure this is the only place where @lsm_attr_names is used,
right? If true, when coupled with the idea that these syscalls are
going to close the door on new LSM attributes in procfs I think we can
just put the mapping directly in this function via a series of
if-statements.
> + return 0;
> +}
> +
> /**
> * sys_lsm_set_self_attr - Set current task's security module attribute
> * @attr: which attribute to set
> diff --git a/security/security.c b/security/security.c
> index 2c57fe28c4f7..f7b814a3940c 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -753,6 +753,37 @@ static int lsm_superblock_alloc(struct super_block *sb)
> return 0;
> }
>
> +/**
> + * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
> + * @ctx: an LSM context to be filled
> + * @context: the new context value
> + * @context_size: the size of the new context value
> + * @id: LSM id
> + * @flags: LSM defined flags
> + *
> + * Fill all of the fields in a user space lsm_ctx structure.
> + * Caller is assumed to have verified that @ctx has enough space
> + * for @context.
> + * Returns 0 on success, -EFAULT on a copyout error.
> + */
> +int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
> + size_t context_size, u64 id, u64 flags)
> +{
> + struct lsm_ctx local;
> + void __user *vc = ctx;
> +
> + local.id = id;
> + local.flags = flags;
> + local.ctx_len = context_size;
> + local.len = context_size + sizeof(local);
> + vc += sizeof(local);
See my prior comments about void pointer math.
> + if (copy_to_user(ctx, &local, sizeof(local)))
> + return -EFAULT;
> + if (context_size > 0 && copy_to_user(vc, context, context_size))
> + return -EFAULT;
Should we handle the padding in this function?
> + return 0;
> +}
--
paul-moore.com
