On 1/11/2023 1:01 PM, Paul Moore wrote:
> On Mon, Jan 9, 2023 at 1:07 PM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote:
>> As LSMs are registered add their lsm_id pointers to a table.
>> This will be used later for attribute reporting.
>>
>> Determine the number of possible security modules based on
>> their respective CONFIG options. This allows the number to be
>> known at build time. This allows data structures and tables
>> to use the constant.
>>
>> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
>> ---
>> include/linux/security.h | 2 ++
>> security/security.c | 44 +++++++++++++++++++++++++++++++++-------
>> 2 files changed, 39 insertions(+), 7 deletions(-)
>>
>> diff --git a/include/linux/security.h b/include/linux/security.h
>> index 5b67f208f7de..33ed1860b96f 100644
>> --- a/include/linux/security.h
>> +++ b/include/linux/security.h
>> @@ -138,6 +138,8 @@ enum lockdown_reason {
>> };
>>
>> extern const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1];
>> +extern u32 lsm_active_cnt;
>> +extern struct lsm_id *lsm_idlist[];
>>
>> /* These functions are in security/commoncap.c */
>> extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
>> diff --git a/security/security.c b/security/security.c
>> index 07a8fe7f92bf..a590fa98ddd6 100644
>> --- a/security/security.c
>> +++ b/security/security.c
>> @@ -28,12 +28,29 @@
>> #include <linux/backing-dev.h>
>> #include <linux/string.h>
>> #include <linux/msg.h>
>> +#include <uapi/linux/lsm.h>
>> #include <net/flow.h>
>>
>> #define MAX_LSM_EVM_XATTR 2
>>
>> -/* How many LSMs were built into the kernel? */
>> -#define LSM_COUNT (__end_lsm_info - __start_lsm_info)
>> +/*
>> + * How many LSMs are built into the kernel as determined at
>> + * build time. Used to determine fixed array sizes.
>> + * The capability module is accounted for by CONFIG_SECURITY
>> + */
>> +#define LSM_COUNT ( \
>> + (IS_ENABLED(CONFIG_SECURITY) ? 1 : 0) + \
>> + (IS_ENABLED(CONFIG_SECURITY_SELINUX) ? 1 : 0) + \
>> + (IS_ENABLED(CONFIG_SECURITY_SMACK) ? 1 : 0) + \
>> + (IS_ENABLED(CONFIG_SECURITY_TOMOYO) ? 1 : 0) + \
>> + (IS_ENABLED(CONFIG_SECURITY_IMA) ? 1 : 0) + \
>> + (IS_ENABLED(CONFIG_SECURITY_APPARMOR) ? 1 : 0) + \
>> + (IS_ENABLED(CONFIG_SECURITY_YAMA) ? 1 : 0) + \
>> + (IS_ENABLED(CONFIG_SECURITY_LOADPIN) ? 1 : 0) + \
>> + (IS_ENABLED(CONFIG_SECURITY_SAFESETID) ? 1 : 0) + \
>> + (IS_ENABLED(CONFIG_SECURITY_LOCKDOWN_LSM) ? 1 : 0) + \
>> + (IS_ENABLED(CONFIG_BPF_LSM) ? 1 : 0) + \
>> + (IS_ENABLED(CONFIG_SECURITY_LANDLOCK) ? 1 : 0))
>>
>> /*
>> * These are descriptions of the reasons that can be passed to the
>> @@ -90,7 +107,7 @@ static __initdata const char *chosen_major_lsm;
>> static __initconst const char * const builtin_lsm_order = CONFIG_LSM;
>>
>> /* Ordered list of LSMs to initialize. */
>> -static __initdata struct lsm_info **ordered_lsms;
>> +static __initdata struct lsm_info *ordered_lsms[LSM_COUNT + 1];
> I'm guessing this 'LSM_COUNT + 1' logic is basically just copied from
> ordered_lsm_init() - which is okay - but can you remind me why it is
> 'LSM_COUNT + 1' and not just 'LSM_COUNT'? Based on the LSM_COUNT
> macro above it seems like LSM_COUNT should be enough, no?
Yup. I didn't spend a lot of time investigating why the + 1.
I'll look more deeply and correct if appropriate.
>> static __initdata struct lsm_info *exclusive;
>>
>> static __initdata bool debug;
>> @@ -341,13 +358,16 @@ static void __init report_lsm_order(void)
>> pr_cont("\n");
>> }
>>
>> +/*
>> + * Current index to use while initializing the lsm id list.
>> + */
>> +u32 lsm_active_cnt __lsm_ro_after_init;
>> +struct lsm_id *lsm_idlist[LSM_COUNT] __lsm_ro_after_init;
>> +
>> static void __init ordered_lsm_init(void)
>> {
>> struct lsm_info **lsm;
>>
>> - ordered_lsms = kcalloc(LSM_COUNT + 1, sizeof(*ordered_lsms),
>> - GFP_KERNEL);
>> -
>> if (chosen_lsm_order) {
>> if (chosen_major_lsm) {
>> pr_warn("security=%s is ignored because it is superseded by lsm=%s\n",
>> @@ -388,7 +408,7 @@ static void __init ordered_lsm_init(void)
>> for (lsm = ordered_lsms; *lsm; lsm++)
>> initialize_lsm(*lsm);
>>
>> - kfree(ordered_lsms);
>> + init_debug("lsm count = %d\n", lsm_active_cnt);
>> }
> Given 86ef3c735ec8 ("LSM: Better reporting of actual LSMs at boot"),
> is this needed?
None of what comes out from lsm.debug is strictly necessary, and
human or script can parse "initializing lsm=", but sometimes the
number of LSMs is interesting.
>
> --
> paul-moore.com
