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Message-ID: <f1816e37-56f5-43de-8a52-129a2952c355@schaufler-ca.com>
Date: Wed, 16 Jul 2025 10:44:43 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: Blaise Boscaccy <bboscaccy@...ux.microsoft.com>,
Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Stephen Smalley <stephen.smalley.work@...il.com>,
Ondrej Mosnacek <omosnace@...hat.com>,
John Johansen <john.johansen@...onical.com>,
Christian Göttsche <cgzones@...glemail.com>,
linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org,
selinux@...r.kernel.org, bpf@...r.kernel.org,
Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH] lsm,selinux: Add LSM blob support for BPF objects
On 7/15/2025 3:25 PM, Blaise Boscaccy wrote:
> This patch introduces LSM blob support for BPF maps, programs, and
> tokens to enable LSM stacking and multiplexing of LSM modules that
> govern BPF objects. Additionally, the existing BPF hooks used by
> SELinux have been updated to utilize the new blob infrastructure,
> removing the assumption of exclusive ownership of the security
> pointer.
>
> Signed-off-by: Blaise Boscaccy <bboscaccy@...ux.microsoft.com>
> ---
> include/linux/lsm_hooks.h | 3 +
> security/security.c | 120 +++++++++++++++++++++++++++++-
> security/selinux/hooks.c | 56 +++-----------
> security/selinux/include/objsec.h | 17 +++++
> 4 files changed, 147 insertions(+), 49 deletions(-)
>
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 090d1d3e19fed..79ec5a2bdcca7 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -116,6 +116,9 @@ struct lsm_blob_sizes {
> int lbs_xattr_count; /* number of xattr slots in new_xattrs array */
> int lbs_tun_dev;
> int lbs_bdev;
> + int lbs_bpf_map;
> + int lbs_bpf_prog;
> + int lbs_bpf_token;
> };
>
> /*
> diff --git a/security/security.c b/security/security.c
> index 596d418185773..8c413b84f33db 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -283,6 +283,9 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed)
> lsm_set_blob_size(&needed->lbs_xattr_count,
> &blob_sizes.lbs_xattr_count);
> lsm_set_blob_size(&needed->lbs_bdev, &blob_sizes.lbs_bdev);
> + lsm_set_blob_size(&needed->lbs_bpf_map, &blob_sizes.lbs_bpf_map);
> + lsm_set_blob_size(&needed->lbs_bpf_prog, &blob_sizes.lbs_bpf_prog);
> + lsm_set_blob_size(&needed->lbs_bpf_token, &blob_sizes.lbs_bpf_token);
> }
>
> /* Prepare LSM for initialization. */
> @@ -480,6 +483,9 @@ static void __init ordered_lsm_init(void)
> init_debug("tun device blob size = %d\n", blob_sizes.lbs_tun_dev);
> init_debug("xattr slots = %d\n", blob_sizes.lbs_xattr_count);
> init_debug("bdev blob size = %d\n", blob_sizes.lbs_bdev);
> + init_debug("bpf map blob size = %d\n", blob_sizes.lbs_bpf_map);
> + init_debug("bpf prog blob size = %d\n", blob_sizes.lbs_bpf_prog);
> + init_debug("bpf token blob size = %d\n", blob_sizes.lbs_bpf_token);
>
> /*
> * Create any kmem_caches needed for blobs
> @@ -835,6 +841,72 @@ static int lsm_bdev_alloc(struct block_device *bdev)
> return 0;
> }
>
> +/**
> + * lsm_bpf_map_alloc - allocate a composite bpf_map blob
> + * @map: the bpf_map that needs a blob
> + *
> + * Allocate the bpf_map blob for all the modules
> + *
> + * Returns 0, or -ENOMEM if memory can't be allocated.
> + */
> +static int lsm_bpf_map_alloc(struct bpf_map *map)
> +{
> + if (blob_sizes.lbs_bpf_map == 0) {
> + map->security = NULL;
> + return 0;
> + }
> +
> + map->security = kzalloc(blob_sizes.lbs_bpf_map, GFP_KERNEL);
Some of the blobs use kmem_cache_alloc(). You should consider if that
might be right for you.
> + if (!map->security)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> +/**
> + * lsm_bpf_prog_alloc - allocate a composite bpf_prog blob
> + * @prog: the bpf_prog that needs a blob
> + *
> + * Allocate the bpf_prog blob for all the modules
> + *
> + * Returns 0, or -ENOMEM if memory can't be allocated.
> + */
> +static int lsm_bpf_prog_alloc(struct bpf_prog *prog)
> +{
> + if (blob_sizes.lbs_bpf_prog == 0) {
> + prog->aux->security = NULL;
> + return 0;
> + }
> +
> + prog->aux->security = kzalloc(blob_sizes.lbs_bpf_prog, GFP_KERNEL);
> + if (!prog->aux->security)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> +/**
> + * lsm_bpf_token_alloc - allocate a composite bpf_token blob
> + * @token: the bpf_token that needs a blob
> + *
> + * Allocate the bpf_token blob for all the modules
> + *
> + * Returns 0, or -ENOMEM if memory can't be allocated.
> + */
> +static int lsm_bpf_token_alloc(struct bpf_token *token)
> +{
> + if (blob_sizes.lbs_bpf_token == 0) {
> + token->security = NULL;
> + return 0;
> + }
> +
> + token->security = kzalloc(blob_sizes.lbs_bpf_token, GFP_KERNEL);
> + if (!token->security)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> /**
> * lsm_early_task - during initialization allocate a composite task blob
> * @task: the task that needs a blob
> @@ -5684,7 +5756,16 @@ int security_bpf_prog(struct bpf_prog *prog)
> int security_bpf_map_create(struct bpf_map *map, union bpf_attr *attr,
> struct bpf_token *token, bool kernel)
> {
> - return call_int_hook(bpf_map_create, map, attr, token, kernel);
> + int rc = 0;
> +
> + rc = lsm_bpf_map_alloc(map);
> + if (unlikely(rc))
> + return rc;
> +
> + rc = call_int_hook(bpf_map_create, map, attr, token, kernel);
> + if (unlikely(rc))
> + security_bpf_map_free(map);
> + return rc;
> }
>
> /**
> @@ -5703,7 +5784,16 @@ int security_bpf_map_create(struct bpf_map *map, union bpf_attr *attr,
> int security_bpf_prog_load(struct bpf_prog *prog, union bpf_attr *attr,
> struct bpf_token *token, bool kernel)
> {
> - return call_int_hook(bpf_prog_load, prog, attr, token, kernel);
> + int rc = 0;
> +
> + rc = lsm_bpf_prog_alloc(prog);
> + if (unlikely(rc))
> + return rc;
> +
> + rc = call_int_hook(bpf_prog_load, prog, attr, token, kernel);
> + if (unlikely(rc))
> + security_bpf_prog_free(prog);
> + return rc;
> }
>
> /**
> @@ -5720,7 +5810,16 @@ int security_bpf_prog_load(struct bpf_prog *prog, union bpf_attr *attr,
> int security_bpf_token_create(struct bpf_token *token, union bpf_attr *attr,
> const struct path *path)
> {
> - return call_int_hook(bpf_token_create, token, attr, path);
> + int rc = 0;
> +
> + rc = lsm_bpf_token_alloc(token);
> + if (unlikely(rc))
> + return rc;
> +
> + rc = call_int_hook(bpf_token_create, token, attr, path);
> + if (unlikely(rc))
> + security_bpf_token_free(token);
> + return rc;
> }
>
> /**
> @@ -5763,7 +5862,12 @@ int security_bpf_token_capable(const struct bpf_token *token, int cap)
> */
> void security_bpf_map_free(struct bpf_map *map)
> {
> + if (!map->security)
> + return;
> +
> call_void_hook(bpf_map_free, map);
> + kfree(map->security);
> + map->security = NULL;
> }
>
> /**
> @@ -5774,7 +5878,12 @@ void security_bpf_map_free(struct bpf_map *map)
> */
> void security_bpf_prog_free(struct bpf_prog *prog)
> {
> + if (!prog->aux->security)
> + return;
> +
> call_void_hook(bpf_prog_free, prog);
> + kfree(prog->aux->security);
> + prog->aux->security = NULL;
> }
>
> /**
> @@ -5785,7 +5894,12 @@ void security_bpf_prog_free(struct bpf_prog *prog)
> */
> void security_bpf_token_free(struct bpf_token *token)
> {
> + if (!token->security)
> + return;
> +
> call_void_hook(bpf_token_free, token);
> + kfree(token->security);
> + token->security = NULL;
> }
> #endif /* CONFIG_BPF_SYSCALL */
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 595ceb314aeb3..8052fb5fafc4d 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -7038,14 +7038,14 @@ static int bpf_fd_pass(const struct file *file, u32 sid)
>
> if (file->f_op == &bpf_map_fops) {
> map = file->private_data;
> - bpfsec = map->security;
> + bpfsec = selinux_bpf_map_security(map);
> ret = avc_has_perm(sid, bpfsec->sid, SECCLASS_BPF,
> bpf_map_fmode_to_av(file->f_mode), NULL);
> if (ret)
> return ret;
> } else if (file->f_op == &bpf_prog_fops) {
> prog = file->private_data;
> - bpfsec = prog->aux->security;
> + bpfsec = selinux_bpf_prog_security(prog);
> ret = avc_has_perm(sid, bpfsec->sid, SECCLASS_BPF,
> BPF__PROG_RUN, NULL);
> if (ret)
> @@ -7059,7 +7059,7 @@ static int selinux_bpf_map(struct bpf_map *map, fmode_t fmode)
> u32 sid = current_sid();
> struct bpf_security_struct *bpfsec;
>
> - bpfsec = map->security;
> + bpfsec = selinux_bpf_map_security(map);
> return avc_has_perm(sid, bpfsec->sid, SECCLASS_BPF,
> bpf_map_fmode_to_av(fmode), NULL);
> }
> @@ -7069,7 +7069,7 @@ static int selinux_bpf_prog(struct bpf_prog *prog)
> u32 sid = current_sid();
> struct bpf_security_struct *bpfsec;
>
> - bpfsec = prog->aux->security;
> + bpfsec = selinux_bpf_prog_security(prog);
> return avc_has_perm(sid, bpfsec->sid, SECCLASS_BPF,
> BPF__PROG_RUN, NULL);
> }
> @@ -7079,69 +7079,33 @@ static int selinux_bpf_map_create(struct bpf_map *map, union bpf_attr *attr,
> {
> struct bpf_security_struct *bpfsec;
>
> - bpfsec = kzalloc(sizeof(*bpfsec), GFP_KERNEL);
> - if (!bpfsec)
> - return -ENOMEM;
> -
> + bpfsec = selinux_bpf_map_security(map);
> bpfsec->sid = current_sid();
> - map->security = bpfsec;
>
> return 0;
> }
>
> -static void selinux_bpf_map_free(struct bpf_map *map)
> -{
> - struct bpf_security_struct *bpfsec = map->security;
> -
> - map->security = NULL;
> - kfree(bpfsec);
> -}
> -
> static int selinux_bpf_prog_load(struct bpf_prog *prog, union bpf_attr *attr,
> struct bpf_token *token, bool kernel)
> {
> struct bpf_security_struct *bpfsec;
>
> - bpfsec = kzalloc(sizeof(*bpfsec), GFP_KERNEL);
> - if (!bpfsec)
> - return -ENOMEM;
> -
> + bpfsec = selinux_bpf_prog_security(prog);
> bpfsec->sid = current_sid();
> - prog->aux->security = bpfsec;
>
> return 0;
> }
>
> -static void selinux_bpf_prog_free(struct bpf_prog *prog)
> -{
> - struct bpf_security_struct *bpfsec = prog->aux->security;
> -
> - prog->aux->security = NULL;
> - kfree(bpfsec);
> -}
> -
> static int selinux_bpf_token_create(struct bpf_token *token, union bpf_attr *attr,
> const struct path *path)
> {
> struct bpf_security_struct *bpfsec;
>
> - bpfsec = kzalloc(sizeof(*bpfsec), GFP_KERNEL);
> - if (!bpfsec)
> - return -ENOMEM;
> -
> + bpfsec = selinux_bpf_token_security(token);
> bpfsec->sid = current_sid();
> - token->security = bpfsec;
>
> return 0;
> }
> -
> -static void selinux_bpf_token_free(struct bpf_token *token)
> -{
> - struct bpf_security_struct *bpfsec = token->security;
> -
> - token->security = NULL;
> - kfree(bpfsec);
> -}
> #endif
>
> struct lsm_blob_sizes selinux_blob_sizes __ro_after_init = {
> @@ -7159,6 +7123,9 @@ struct lsm_blob_sizes selinux_blob_sizes __ro_after_init = {
> .lbs_xattr_count = SELINUX_INODE_INIT_XATTRS,
> .lbs_tun_dev = sizeof(struct tun_security_struct),
> .lbs_ib = sizeof(struct ib_security_struct),
> + .lbs_bpf_map = sizeof(struct bpf_security_struct),
> + .lbs_bpf_prog = sizeof(struct bpf_security_struct),
> + .lbs_bpf_token = sizeof(struct bpf_security_struct),
> };
>
> #ifdef CONFIG_PERF_EVENTS
> @@ -7510,9 +7477,6 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
> LSM_HOOK_INIT(bpf, selinux_bpf),
> LSM_HOOK_INIT(bpf_map, selinux_bpf_map),
> LSM_HOOK_INIT(bpf_prog, selinux_bpf_prog),
> - LSM_HOOK_INIT(bpf_map_free, selinux_bpf_map_free),
> - LSM_HOOK_INIT(bpf_prog_free, selinux_bpf_prog_free),
> - LSM_HOOK_INIT(bpf_token_free, selinux_bpf_token_free),
> #endif
>
> #ifdef CONFIG_PERF_EVENTS
> diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h
> index 6ee7dc4dfd6e0..9f935ed9a761f 100644
> --- a/security/selinux/include/objsec.h
> +++ b/security/selinux/include/objsec.h
> @@ -26,6 +26,7 @@
> #include <linux/lsm_hooks.h>
> #include <linux/msg.h>
> #include <net/net_namespace.h>
> +#include <linux/bpf.h>
> #include "flask.h"
> #include "avc.h"
>
> @@ -237,4 +238,20 @@ selinux_perf_event(void *perf_event)
> return perf_event + selinux_blob_sizes.lbs_perf_event;
> }
>
> +#ifdef CONFIG_BPF_SYSCALL
> +static inline struct bpf_security_struct *selinux_bpf_map_security(struct bpf_map *map)
> +{
> + return map->security + selinux_blob_sizes.lbs_bpf_map;
> +}
> +
> +static inline struct bpf_security_struct *selinux_bpf_prog_security(struct bpf_prog *prog)
> +{
> + return prog->aux->security + selinux_blob_sizes.lbs_bpf_prog;
> +}
> +
> +static inline struct bpf_security_struct *selinux_bpf_token_security(struct bpf_token *token)
> +{
> + return token->security + selinux_blob_sizes.lbs_bpf_token;
> +}
> +#endif /* CONFIG_BPF_SYSCALL */
> #endif /* _SELINUX_OBJSEC_H_ */
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