[PATCH v4 04/23] LSM: Create and manage the lsmblob data structure.
John Johansen
john.johansen at canonical.com
Wed Jun 26 23:39:20 UTC 2019
On 6/26/19 12:22 PM, Casey Schaufler wrote:
> When more than one security module is exporting data to
> audit and networking sub-systems a single 32 bit integer
> is no longer sufficient to represent the data. Add a
> structure to be used instead.
>
> The lsmblob structure is currently an array of
> u32 "secids". There is an entry for each of the
> security modules built into the system that would
> use secids if active. The system assigns the module
> a "slot" when it registers hooks. If modules are
> compiled in but not registered there will be unused
> slots.
>
> A new lsm_id structure, which contains the name
> of the LSM and its slot number, is created. There
> is an instance for each LSM, which assigns the name
> and passes it to the infrastructure to set the slot.
>
> Signed-off-by: Casey Schaufler <casey at schaufler-ca.com>
> ---
> include/linux/lsm_hooks.h | 12 +++++--
> include/linux/security.h | 66 ++++++++++++++++++++++++++++++++++++++
> security/apparmor/lsm.c | 4 ++-
> security/commoncap.c | 7 +++-
> security/loadpin/loadpin.c | 8 ++++-
> security/safesetid/lsm.c | 8 ++++-
> security/security.c | 31 ++++++++++++++----
> security/selinux/hooks.c | 5 ++-
> security/smack/smack_lsm.c | 4 ++-
> security/tomoyo/tomoyo.c | 8 ++++-
> security/yama/yama_lsm.c | 4 ++-
> 11 files changed, 140 insertions(+), 17 deletions(-)
>
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 3fe39abccc8f..fe1fb7a69ee5 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -2029,6 +2029,14 @@ struct security_hook_heads {
> #endif /* CONFIG_BPF_SYSCALL */
> } __randomize_layout;
>
> +/*
> + * Information that identifies a security module.
> + */
> +struct lsm_id {
> + const char *lsm; /* Name of the LSM */
> + int slot; /* Slot in lsmblob if one is allocated */
> +};
> +
> /*
> * Security module hook list structure.
> * For use with generic list macros for common operations.
> @@ -2037,7 +2045,7 @@ struct security_hook_list {
> struct hlist_node list;
> struct hlist_head *head;
> union security_list_options hook;
> - char *lsm;
> + struct lsm_id *lsmid;
> } __randomize_layout;
>
> /*
> @@ -2068,7 +2076,7 @@ extern struct security_hook_heads security_hook_heads;
> extern char *lsm_names;
>
> extern void security_add_hooks(struct security_hook_list *hooks, int count,
> - char *lsm);
> + struct lsm_id *lsmid);
>
> #define LSM_FLAG_LEGACY_MAJOR BIT(0)
> #define LSM_FLAG_EXCLUSIVE BIT(1)
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 49f2685324b0..5bb8b9a6fa84 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -76,6 +76,72 @@ enum lsm_event {
> LSM_POLICY_CHANGE,
> };
>
> +/*
> + * Data exported by the security modules
> + *
> + * Any LSM that provides secid or secctx based hooks must be included.
> + */
> +#define LSMBLOB_ENTRIES ( \
> + (IS_ENABLED(CONFIG_SECURITY_SELINUX) ? 1 : 0) + \
> + (IS_ENABLED(CONFIG_SECURITY_SMACK) ? 1 : 0) + \
> + (IS_ENABLED(CONFIG_SECURITY_APPARMOR) ? 1 : 0))
> +
> +struct lsmblob {
> + u32 secid[LSMBLOB_ENTRIES];
> +};
> +
> +#define LSMBLOB_INVALID -1 /* Not a valid LSM slot number */
> +#define LSMBLOB_NEEDED -2 /* Slot requested on initialization */
> +#define LSMBLOB_NOT_NEEDED -3 /* Slot not requested */
> +
> +/**
> + * lsmblob_init - initialize an lsmblob structure.
> + * @blob: Pointer to the data to initialize
> + * @secid: The initial secid value
> + *
> + * Set all secid for all modules to the specified value.
> + */
> +static inline void lsmblob_init(struct lsmblob *blob, u32 secid)
> +{
> + int i;
> +
> + for (i = 0; i < LSMBLOB_ENTRIES; i++)
> + blob->secid[i] = secid;
> +}
> +
> +/**
> + * lsmblob_is_set - report if there is an value in the lsmblob
> + * @blob: Pointer to the exported LSM data
> + *
> + * Returns true if there is a secid set, false otherwise
> + */
> +static inline bool lsmblob_is_set(struct lsmblob *blob)
> +{
> + int i;
> +
> + for (i = 0; i < LSMBLOB_ENTRIES; i++)
> + if (blob->secid[i] != 0)
> + return true;
> + return false;
> +}
> +
> +/**
> + * lsmblob_equal - report if the two lsmblob's are equal
> + * @bloba: Pointer to one LSM data
> + * @blobb: Pointer to the other LSM data
> + *
> + * Returns true if all entries in the two are equal, false otherwise
> + */
> +static inline bool lsmblob_equal(struct lsmblob *bloba, struct lsmblob *blobb)
> +{
> + int i;
> +
> + for (i = 0; i < LSMBLOB_ENTRIES; i++)
> + if (bloba->secid[i] != blobb->secid[i])
> + return false;
> + return true;
> +}
> +
> /* These functions are in security/commoncap.c */
> extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
> int cap, unsigned int opts);
> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> index 2716e7731279..6d2eefc9b7c1 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -1138,6 +1138,8 @@ struct lsm_blob_sizes apparmor_blob_sizes __lsm_ro_after_init = {
> .lbs_sock = sizeof(struct aa_sk_ctx),
> };
>
> +static struct lsm_id apparmor_lsmid = { .lsm="apparmor", .slot=LSMBLOB_NEEDED };
__lsm_ro_after_init
> +
> static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(ptrace_access_check, apparmor_ptrace_access_check),
> LSM_HOOK_INIT(ptrace_traceme, apparmor_ptrace_traceme),
> @@ -1679,7 +1681,7 @@ static int __init apparmor_init(void)
> goto buffers_out;
> }
> security_add_hooks(apparmor_hooks, ARRAY_SIZE(apparmor_hooks),
> - "apparmor");
> + &apparmor_lsmid);
>
> /* Report that AppArmor successfully initialized */
> apparmor_initialized = 1;
> diff --git a/security/commoncap.c b/security/commoncap.c
> index afd9679ca866..305a6088c81e 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -1344,6 +1344,11 @@ int cap_mmap_file(struct file *file, unsigned long reqprot,
>
> #ifdef CONFIG_SECURITY
>
> +static struct lsm_id capability_lsmid = {
__lsm_ro_after_init
> + .lsm="capability",
> + .slot=LSMBLOB_NOT_NEEDED
> +};
> +
> static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(capable, cap_capable),
> LSM_HOOK_INIT(settime, cap_settime),
> @@ -1368,7 +1373,7 @@ static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
> static int __init capability_init(void)
> {
> security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
> - "capability");
> + &capability_lsmid);
> return 0;
> }
>
> diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
> index 055fb0a64169..13db59d5327e 100644
> --- a/security/loadpin/loadpin.c
> +++ b/security/loadpin/loadpin.c
> @@ -181,6 +181,11 @@ static int loadpin_load_data(enum kernel_load_data_id id)
> return loadpin_read_file(NULL, (enum kernel_read_file_id) id);
> }
>
> +static struct lsm_id loadpin_lsmid = {
__lsm_ro_after_init
> + .lsm="loadpin",
> + .slot=LSMBLOB_NOT_NEEDED
> +};
> +
> static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(sb_free_security, loadpin_sb_free_security),
> LSM_HOOK_INIT(kernel_read_file, loadpin_read_file),
> @@ -191,7 +196,8 @@ static int __init loadpin_init(void)
> {
> pr_info("ready to pin (currently %senforcing)\n",
> enforce ? "" : "not ");
> - security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), "loadpin");
> + security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks),
> + &loadpin_lsmid);
> return 0;
> }
>
> diff --git a/security/safesetid/lsm.c b/security/safesetid/lsm.c
> index cecd38e2ac80..ca34badde4cf 100644
> --- a/security/safesetid/lsm.c
> +++ b/security/safesetid/lsm.c
> @@ -255,6 +255,11 @@ void flush_safesetid_whitelist_entries(void)
> }
> }
>
> +static struct lsm_id safesetid_lsmid = {
__lsm_ro_after_init
> + .lsm="safesetid",
> + .slot=LSMBLOB_NOT_NEEDED
> +};
> +
> static struct security_hook_list safesetid_security_hooks[] = {
> LSM_HOOK_INIT(task_fix_setuid, safesetid_task_fix_setuid),
> LSM_HOOK_INIT(capable, safesetid_security_capable)
> @@ -263,7 +268,8 @@ static struct security_hook_list safesetid_security_hooks[] = {
> static int __init safesetid_security_init(void)
> {
> security_add_hooks(safesetid_security_hooks,
> - ARRAY_SIZE(safesetid_security_hooks), "safesetid");
> + ARRAY_SIZE(safesetid_security_hooks),
> + &safesetid_lsmid);
>
> /* Report that SafeSetID successfully initialized */
> safesetid_initialized = 1;
> diff --git a/security/security.c b/security/security.c
> index 7cfedb90210a..27e2db3d6b04 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -317,6 +317,7 @@ static void __init ordered_lsm_init(void)
> init_debug("sock blob size = %d\n", blob_sizes.lbs_sock);
> init_debug("superblock blob size = %d\n", blob_sizes.lbs_superblock);
> init_debug("task blob size = %d\n", blob_sizes.lbs_task);
> + init_debug("lsmblob size = %lu\n", sizeof(struct lsmblob));
>
> /*
> * Create any kmem_caches needed for blobs
> @@ -399,7 +400,7 @@ static bool match_last_lsm(const char *list, const char *lsm)
> return !strcmp(last, lsm);
> }
>
> -static int lsm_append(char *new, char **result)
> +static int lsm_append(const char *new, char **result)
> {
> char *cp;
>
> @@ -420,24 +421,40 @@ static int lsm_append(char *new, char **result)
> return 0;
> }
>
> +/*
> + * Current index to use while initializing the lsmblob secid list.
> + */
> +static int lsm_slot __initdata;
> +
> /**
> * security_add_hooks - Add a modules hooks to the hook lists.
> * @hooks: the hooks to add
> * @count: the number of hooks to add
> - * @lsm: the name of the security module
> + * @lsmid: the identification information for the security module
> *
> * Each LSM has to register its hooks with the infrastructure.
> + * If the LSM is using hooks that export secids allocate a slot
> + * for it in the lsmblob.
> */
> void __init security_add_hooks(struct security_hook_list *hooks, int count,
> - char *lsm)
> + struct lsm_id *lsmid)
> {
> int i;
>
> + if (lsmid->slot == LSMBLOB_NEEDED) {
> + if (lsm_slot >= LSMBLOB_ENTRIES)
> + panic("%s Too many LSMs registered.\n", __func__);
> + lsmid->slot = lsm_slot++;
> + init_debug("%s assigned lsmblob slot %d\n", lsmid->lsm,
> + lsmid->slot);
> + }
It might be nice (but not required) to add back in the list of hooks that need
secids as a cross check of LSMLOB_NOT_NEEDED. It would allow us to catch
bad registrations upfront instead of crashing the kernel when the hook gets
used.
> +
> for (i = 0; i < count; i++) {
> - hooks[i].lsm = lsm;
> + hooks[i].lsmid = lsmid;
> hlist_add_tail_rcu(&hooks[i].list, hooks[i].head);
> }
> - if (lsm_append(lsm, &lsm_names) < 0)
> +
> + if (lsm_append(lsmid->lsm, &lsm_names) < 0)
> panic("%s - Cannot get early memory.\n", __func__);
> }
>
> @@ -1917,7 +1934,7 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
> struct security_hook_list *hp;
>
> hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
> - if (lsm != NULL && strcmp(lsm, hp->lsm))
> + if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm))
> continue;
> return hp->hook.getprocattr(p, name, value);
> }
> @@ -1930,7 +1947,7 @@ int security_setprocattr(const char *lsm, const char *name, void *value,
> struct security_hook_list *hp;
>
> hlist_for_each_entry(hp, &security_hook_heads.setprocattr, list) {
> - if (lsm != NULL && strcmp(lsm, hp->lsm))
> + if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm))
> continue;
> return hp->hook.setprocattr(name, value, size);
> }
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index c83ec2652eda..8c93b07bb353 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -6622,6 +6622,8 @@ struct lsm_blob_sizes selinux_blob_sizes __lsm_ro_after_init = {
> .lbs_superblock = sizeof(struct superblock_security_struct),
> };
>
> +static struct lsm_id selinux_lsmid = { .lsm="selinux", .slot=LSMBLOB_NEEDED };
> +
> static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(binder_set_context_mgr, selinux_binder_set_context_mgr),
> LSM_HOOK_INIT(binder_transaction, selinux_binder_transaction),
> @@ -6877,7 +6879,8 @@ static __init int selinux_init(void)
>
> hashtab_cache_init();
>
> - security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks), "selinux");
> + security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks),
> + &selinux_lsmid);
>
> if (avc_add_callback(selinux_netcache_avc_callback, AVC_CALLBACK_RESET))
> panic("SELinux: Unable to register AVC netcache callback\n");
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index e9560b078efe..ad646b865295 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -4553,6 +4553,8 @@ struct lsm_blob_sizes smack_blob_sizes __lsm_ro_after_init = {
> .lbs_superblock = sizeof(struct superblock_smack),
> };
>
> +static struct lsm_id smack_lsmid = { .lsm="smack", .slot=LSMBLOB_NEEDED };
__lsm_ro_after_init
> +
> static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(ptrace_access_check, smack_ptrace_access_check),
> LSM_HOOK_INIT(ptrace_traceme, smack_ptrace_traceme),
> @@ -4743,7 +4745,7 @@ static __init int smack_init(void)
> /*
> * Register with LSM
> */
> - security_add_hooks(smack_hooks, ARRAY_SIZE(smack_hooks), "smack");
> + security_add_hooks(smack_hooks, ARRAY_SIZE(smack_hooks), &smack_lsmid);
> smack_enabled = 1;
>
> pr_info("Smack: Initializing.\n");
> diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
> index 716c92ec941a..57e6b845ea51 100644
> --- a/security/tomoyo/tomoyo.c
> +++ b/security/tomoyo/tomoyo.c
> @@ -529,6 +529,11 @@ static void tomoyo_task_free(struct task_struct *task)
> }
> }
>
> +static struct lsm_id tomoyo_lsmid = {
__lsm_ro_after_init
> + .lsm="tomoyo",
> + .slot=LSMBLOB_NOT_NEEDED
> +};
> +
> /*
> * tomoyo_security_ops is a "struct security_operations" which is used for
> * registering TOMOYO.
> @@ -581,7 +586,8 @@ static int __init tomoyo_init(void)
> struct tomoyo_task *s = tomoyo_task(current);
>
> /* register ourselves with the security framework */
> - security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks), "tomoyo");
> + security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks),
> + &tomoyo_lsmid);
> pr_info("TOMOYO Linux initialized\n");
> s->domain_info = &tomoyo_kernel_domain;
> atomic_inc(&tomoyo_kernel_domain.users);
> diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
> index efac68556b45..2263822a4af7 100644
> --- a/security/yama/yama_lsm.c
> +++ b/security/yama/yama_lsm.c
> @@ -425,6 +425,8 @@ static int yama_ptrace_traceme(struct task_struct *parent)
> return rc;
> }
>
> +static struct lsm_id yama_lsmid = { .lsm="yama", .slot=LSMBLOB_NOT_NEEDED };
__lsm_ro_after_init
> +
> static struct security_hook_list yama_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(ptrace_access_check, yama_ptrace_access_check),
> LSM_HOOK_INIT(ptrace_traceme, yama_ptrace_traceme),
> @@ -482,7 +484,7 @@ static inline void yama_init_sysctl(void) { }
> static int __init yama_init(void)
> {
> pr_info("Yama: becoming mindful.\n");
> - security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks), "yama");
> + security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks), &yama_lsmid);
> yama_init_sysctl();
> return 0;
> }
>
I like the change,
Reviewed-by: John Johansen <john.johansen at canonical.com>
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