[PATCH 4/6] LSM: Infrastructure management of the dev_tun blob
John Johansen
john.johansen at canonical.com
Tue Jul 9 23:01:37 UTC 2024
On 7/8/24 14:39, Casey Schaufler wrote:
> Move management of the dev_tun security blob out of the individual
> security modules and into the LSM infrastructure. The security modules
> tell the infrastructure how much space they require at initialization.
>
> Signed-off-by: Casey Schaufler <casey at schaufler-ca.com>
one issue below, besides Paul's point the rest of it looks good
> ---
> include/linux/lsm_hook_defs.h | 2 +-
> include/linux/lsm_hooks.h | 1 +
> security/security.c | 11 ++++++++++-
> security/selinux/hooks.c | 22 ++++++----------------
> security/selinux/include/objsec.h | 6 ++++++
> 5 files changed, 24 insertions(+), 18 deletions(-)
>
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 44488b1ab9a9..601e3092a7ed 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -352,7 +352,7 @@ LSM_HOOK(void, LSM_RET_VOID, secmark_refcount_inc, void)
> LSM_HOOK(void, LSM_RET_VOID, secmark_refcount_dec, void)
> LSM_HOOK(void, LSM_RET_VOID, req_classify_flow, const struct request_sock *req,
> struct flowi_common *flic)
> -LSM_HOOK(int, 0, tun_dev_alloc_security, void **security)
> +LSM_HOOK(int, 0, tun_dev_alloc_security, void *security)
> LSM_HOOK(void, LSM_RET_VOID, tun_dev_free_security, void *security)
> LSM_HOOK(int, 0, tun_dev_create, void)
> LSM_HOOK(int, 0, tun_dev_attach_queue, void *security)
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 7233bc0737be..0ff14ff128c8 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -80,6 +80,7 @@ struct lsm_blob_sizes {
> int lbs_msg_msg;
> int lbs_task;
> int lbs_xattr_count; /* number of xattr slots in new_xattrs array */
> + int lbs_tun_dev;
> };
>
> /**
> diff --git a/security/security.c b/security/security.c
> index 438ec6708eb3..2c9d075f5f92 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -234,6 +234,7 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed)
> lsm_set_blob_size(&needed->lbs_sock, &blob_sizes.lbs_sock);
> lsm_set_blob_size(&needed->lbs_superblock, &blob_sizes.lbs_superblock);
> lsm_set_blob_size(&needed->lbs_task, &blob_sizes.lbs_task);
> + lsm_set_blob_size(&needed->lbs_tun_dev, &blob_sizes.lbs_tun_dev);
> lsm_set_blob_size(&needed->lbs_xattr_count,
> &blob_sizes.lbs_xattr_count);
> }
> @@ -412,6 +413,7 @@ 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("tun device blob size = %d\n", blob_sizes.lbs_tun_dev);
> init_debug("xattr slots = %d\n", blob_sizes.lbs_xattr_count);
>
> /*
> @@ -4851,7 +4853,13 @@ EXPORT_SYMBOL(security_secmark_refcount_dec);
> */
> int security_tun_dev_alloc_security(void **security)
> {
> - return call_int_hook(tun_dev_alloc_security, security);
> + int rc;
> +
> + rc = lsm_blob_alloc(security, blob_sizes.lbs_tun_dev, GFP_KERNEL);
> + if (rc)
> + return rc;
> +
> + return call_int_hook(tun_dev_alloc_security, *security);
we either need to free the blob here or make a change to tun_net_init.
if security_tun_dev_alloc fails it is not calling the corresponding
security_tun_dev_free_security()
> }
> EXPORT_SYMBOL(security_tun_dev_alloc_security);
>
> @@ -4864,6 +4872,7 @@ EXPORT_SYMBOL(security_tun_dev_alloc_security);
> void security_tun_dev_free_security(void *security)
> {
> call_void_hook(tun_dev_free_security, security);
> + kfree(security);
> }
> EXPORT_SYMBOL(security_tun_dev_free_security);
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index b3de2e941ef7..7f1d8358922a 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -5573,24 +5573,14 @@ static void selinux_req_classify_flow(const struct request_sock *req,
> flic->flowic_secid = req->secid;
> }
>
> -static int selinux_tun_dev_alloc_security(void **security)
> +static int selinux_tun_dev_alloc_security(void *security)
> {
> - struct tun_security_struct *tunsec;
> + struct tun_security_struct *tunsec = selinux_tun_dev(security);
>
> - tunsec = kzalloc(sizeof(*tunsec), GFP_KERNEL);
> - if (!tunsec)
> - return -ENOMEM;
> tunsec->sid = current_sid();
> -
> - *security = tunsec;
> return 0;
> }
>
> -static void selinux_tun_dev_free_security(void *security)
> -{
> - kfree(security);
> -}
> -
> static int selinux_tun_dev_create(void)
> {
> u32 sid = current_sid();
> @@ -5608,7 +5598,7 @@ static int selinux_tun_dev_create(void)
>
> static int selinux_tun_dev_attach_queue(void *security)
> {
> - struct tun_security_struct *tunsec = security;
> + struct tun_security_struct *tunsec = selinux_tun_dev(security);
>
> return avc_has_perm(current_sid(), tunsec->sid, SECCLASS_TUN_SOCKET,
> TUN_SOCKET__ATTACH_QUEUE, NULL);
> @@ -5616,7 +5606,7 @@ static int selinux_tun_dev_attach_queue(void *security)
>
> static int selinux_tun_dev_attach(struct sock *sk, void *security)
> {
> - struct tun_security_struct *tunsec = security;
> + struct tun_security_struct *tunsec = selinux_tun_dev(security);
> struct sk_security_struct *sksec = selinux_sock(sk);
>
> /* we don't currently perform any NetLabel based labeling here and it
> @@ -5634,7 +5624,7 @@ static int selinux_tun_dev_attach(struct sock *sk, void *security)
>
> static int selinux_tun_dev_open(void *security)
> {
> - struct tun_security_struct *tunsec = security;
> + struct tun_security_struct *tunsec = selinux_tun_dev(security);
> u32 sid = current_sid();
> int err;
>
> @@ -6975,6 +6965,7 @@ struct lsm_blob_sizes selinux_blob_sizes __ro_after_init = {
> .lbs_sock = sizeof(struct sk_security_struct),
> .lbs_superblock = sizeof(struct superblock_security_struct),
> .lbs_xattr_count = SELINUX_INODE_INIT_XATTRS,
> + .lbs_tun_dev = sizeof(struct tun_security_struct),
> };
>
> #ifdef CONFIG_PERF_EVENTS
> @@ -7285,7 +7276,6 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
> LSM_HOOK_INIT(secmark_refcount_inc, selinux_secmark_refcount_inc),
> LSM_HOOK_INIT(secmark_refcount_dec, selinux_secmark_refcount_dec),
> LSM_HOOK_INIT(req_classify_flow, selinux_req_classify_flow),
> - LSM_HOOK_INIT(tun_dev_free_security, selinux_tun_dev_free_security),
> LSM_HOOK_INIT(tun_dev_create, selinux_tun_dev_create),
> LSM_HOOK_INIT(tun_dev_attach_queue, selinux_tun_dev_attach_queue),
> LSM_HOOK_INIT(tun_dev_attach, selinux_tun_dev_attach),
> diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h
> index 83b9443d6919..461c6985977d 100644
> --- a/security/selinux/include/objsec.h
> +++ b/security/selinux/include/objsec.h
> @@ -207,4 +207,10 @@ static inline struct sk_security_struct *selinux_sock(const struct sock *sock)
> return sock->sk_security + selinux_blob_sizes.lbs_sock;
> }
>
> +static inline struct tun_security_struct *
> +selinux_tun_dev(void *security)
> +{
> + return security + selinux_blob_sizes.lbs_tun_dev;
> +}
> +
> #endif /* _SELINUX_OBJSEC_H_ */
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