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Message-ID: <206971d6-70c7-e217-299f-1884310afa15@digikod.net>
Date: Sat, 22 May 2021 10:39:01 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Casey Schaufler <casey@...aufler-ca.com>,
casey.schaufler@...el.com, jmorris@...ei.org,
linux-security-module@...r.kernel.org, selinux@...r.kernel.org
Cc: linux-audit@...hat.com, keescook@...omium.org,
john.johansen@...onical.com, penguin-kernel@...ove.sakura.ne.jp,
paul@...l-moore.com, sds@...ho.nsa.gov,
linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v26 02/25] LSM: Add the lsmblob data structure.
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@...ho.nsa.gov>
> Acked-by: Paul Moore <paul@...l-moore.com>
> Acked-by: John Johansen <john.johansen@...onical.com>
> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
> Cc: <bpf@...r.kernel.org>
> Cc: linux-audit@...hat.com
> Cc: linux-security-module@...r.kernel.org
> Cc: selinux@...r.kernel.org
> To: Mimi Zohar <zohar@...ux.ibm.com>
> To: Mickaël Salaün <mic@...ux.microsoft.com>
> ---
> 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,
You can run the Landlock tests please?
make -C tools/testing/selftests TARGETS=landlock gen_tar
tar -xf kselftest.tar.gz && ./run_kselftest.sh
> +};
> +
> 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?
> + 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);
> }
>
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