LSM: Helpers for attribute names and filling lsm_ctx

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.

Both are used in module specific components of LSM system calls.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Casey Schaufler 2023-09-12 13:56:52 -07:00 committed by Paul Moore
parent 5f42375904
commit e1ca7129db
3 changed files with 79 additions and 0 deletions

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@ -32,6 +32,7 @@
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/sockptr.h>
#include <uapi/linux/lsm.h>
struct linux_binprm;
struct cred;
@ -264,6 +265,7 @@ int unregister_blocking_lsm_notifier(struct notifier_block *nb);
/* prototypes */
extern int security_init(void);
extern int early_security_init(void);
extern u64 lsm_name_to_attr(const char *name);
/* Security operations */
int security_binder_set_context_mgr(const struct cred *mgr);
@ -490,6 +492,8 @@ 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_locked_down(enum lockdown_reason what);
int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
size_t context_size, u64 id, u64 flags);
#else /* CONFIG_SECURITY */
static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
@ -507,6 +511,11 @@ static inline int unregister_blocking_lsm_notifier(struct notifier_block *nb)
return 0;
}
static inline u64 lsm_name_to_attr(const char *name)
{
return LSM_ATTR_UNDEF;
}
static inline void security_free_mnt_opts(void **mnt_opts)
{
}
@ -1415,6 +1424,11 @@ static inline int security_locked_down(enum lockdown_reason what)
{
return 0;
}
static inline int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
size_t context_size, u64 id, u64 flags)
{
return -EOPNOTSUPP;
}
#endif /* CONFIG_SECURITY */
#if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)

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@ -17,6 +17,30 @@
#include <linux/lsm_hooks.h>
#include <uapi/linux/lsm.h>
/**
* lsm_name_to_attr - map an LSM attribute name to its ID
* @name: name of the attribute
*
* Returns the LSM attribute value associated with @name, or 0 if
* there is no mapping.
*/
u64 lsm_name_to_attr(const char *name)
{
if (!strcmp(name, "current"))
return LSM_ATTR_CURRENT;
if (!strcmp(name, "exec"))
return LSM_ATTR_EXEC;
if (!strcmp(name, "fscreate"))
return LSM_ATTR_FSCREATE;
if (!strcmp(name, "keycreate"))
return LSM_ATTR_KEYCREATE;
if (!strcmp(name, "prev"))
return LSM_ATTR_PREV;
if (!strcmp(name, "sockcreate"))
return LSM_ATTR_SOCKCREATE;
return LSM_ATTR_UNDEF;
}
/**
* sys_lsm_set_self_attr - Set current task's security module attribute
* @attr: which attribute to set

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@ -771,6 +771,47 @@ 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, -ENOMEM
* if memory can't be allocated.
*/
int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
size_t context_size, u64 id, u64 flags)
{
struct lsm_ctx *lctx;
size_t locallen = struct_size(lctx, ctx, context_size);
int rc = 0;
lctx = kzalloc(locallen, GFP_KERNEL);
if (lctx == NULL)
return -ENOMEM;
lctx->id = id;
lctx->flags = flags;
lctx->ctx_len = context_size;
lctx->len = locallen;
memcpy(lctx->ctx, context, context_size);
if (copy_to_user(ctx, lctx, locallen))
rc = -EFAULT;
kfree(lctx);
return rc;
}
/*
* The default value of the LSM hook is defined in linux/lsm_hook_defs.h and
* can be accessed with: