Re: [PATCH v26 02/25] LSM: Add the lsmblob data structure.

On 5/22/2021 1:39 AM, Mickaël Salaün wrote: > I like this design but there is an issue with Landlock though, see below. > > On 13/05/2021 22:07, 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. >> >> The audit rules data is expanded to use an array of >> security module data rather than a single instance. >> Because IMA uses the audit rule functions it is >> affected as well. >> >> Acked-by: Stephen Smalley <sds(a)tycho.nsa.gov&gt; >> Acked-by: Paul Moore <paul(a)paul-moore.com&gt; >> Acked-by: John Johansen <john.johansen(a)canonical.com&gt; >> Signed-off-by: Casey Schaufler <casey(a)schaufler-ca.com&gt; >> Cc: <bpf(a)vger.kernel.org&gt; >> Cc: linux-audit(a)redhat.com >> Cc: linux-security-module(a)vger.kernel.org >> Cc: selinux(a)vger.kernel.org >> To: Mimi Zohar <zohar(a)linux.ibm.com&gt; >> To: Mickaël Salaün <mic(a)linux.microsoft.com&gt; >> --- >> include/linux/audit.h | 4 +- >> include/linux/lsm_hooks.h | 12 ++++- >> include/linux/security.h | 67 +++++++++++++++++++++++++-- >> kernel/auditfilter.c | 24 +++++----- >> kernel/auditsc.c | 13 +++--- >> security/apparmor/lsm.c | 7 ++- >> security/bpf/hooks.c | 12 ++++- >> security/commoncap.c | 7 ++- >> security/integrity/ima/ima_policy.c | 40 +++++++++++----- >> security/landlock/cred.c | 2 +- >> security/landlock/fs.c | 2 +- >> security/landlock/ptrace.c | 2 +- >> security/landlock/setup.c | 4 ++ >> security/landlock/setup.h | 1 + >> security/loadpin/loadpin.c | 8 +++- >> security/lockdown/lockdown.c | 7 ++- >> security/safesetid/lsm.c | 8 +++- >> security/security.c | 72 ++++++++++++++++++++++++----- >> security/selinux/hooks.c | 8 +++- >> security/smack/smack_lsm.c | 7 ++- >> security/tomoyo/tomoyo.c | 8 +++- >> security/yama/yama_lsm.c | 7 ++- >> 22 files changed, 262 insertions(+), 60 deletions(-) >> > [...] > >> diff --git a/security/landlock/setup.c b/security/landlock/setup.c >> index f8e8e980454c..4a12666a4090 100644 >> --- a/security/landlock/setup.c >> +++ b/security/landlock/setup.c >> @@ -23,6 +23,10 @@ struct lsm_blob_sizes landlock_blob_sizes __lsm_ro_after_init = { >> .lbs_superblock = sizeof(struct landlock_superblock_security), >> }; >> >> +struct lsm_id landlock_lsmid __lsm_ro_after_init = { >> + .lsm = LANDLOCK_NAME, > It is missing: .slot = LSMBLOB_NEEDED, Sorry for the delay. Landlock does not provide any of the hooks that use a struct lsmblob. That would be secid_to_secctx, secctx_to_secid, inode_getsecid, cred_getsecid, kernel_act_as task_getsecid_subj task_getsecid_obj and ipc_getsecid. Setting .slot = LSMBLOB_NEEDED indicates that the LSM uses a slot in struct lsmblob. Landlock does not need a slot.

> > You can run the Landlock tests please? > make -C tools/testing/selftests TARGETS=landlock gen_tar > tar -xf kselftest.tar.gz && ./run_kselftest.sh Sure. I'll add them to my routine.

> > >> +}; >> + >> static int __init landlock_init(void) >> { >> landlock_add_cred_hooks(); > [...] > >> diff --git a/security/security.c b/security/security.c >> index e12a7c463468..a3276deb1b8a 100644 >> --- a/security/security.c >> +++ b/security/security.c >> @@ -344,6 +344,7 @@ 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 = %zu\n", sizeof(struct lsmblob)); >> >> /* >> * Create any kmem_caches needed for blobs >> @@ -471,21 +472,36 @@ static int lsm_append(const char *new, char **result) >> return 0; >> } >> >> +/* >> + * Current index to use while initializing the lsmblob secid list. >> + */ >> +static int lsm_slot __lsm_ro_after_init; >> + >> /** >> * 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; >> > Could you add a WARN_ON(!lsmid->slot || !lsmid->name) here? Yes. That's reasonable.

> > >> + 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); >> + } >> + >> for (i = 0; i < count; i++) { >> - hooks[i].lsm = lsm; >> + hooks[i].lsmid = lsmid; >> hlist_add_tail_rcu(&hooks[i].list, hooks[i].head); >> } >>