[PATCH net-next v7 4/5] selinux: bpf: Add selinux check for eBPF syscall operations
Paul Moore
paul at paul-moore.com
Mon Oct 23 23:27:57 UTC 2017
On Wed, Oct 18, 2017 at 4:00 PM, Chenbo Feng
<chenbofeng.kernel at gmail.com> wrote:
> From: Chenbo Feng <fengc at google.com>
>
> Implement the actual checks introduced to eBPF related syscalls. This
> implementation use the security field inside bpf object to store a sid that
> identify the bpf object. And when processes try to access the object,
> selinux will check if processes have the right privileges. The creation
> of eBPF object are also checked at the general bpf check hook and new
> cmd introduced to eBPF domain can also be checked there.
>
> Signed-off-by: Chenbo Feng <fengc at google.com>
> Acked-by: Alexei Starovoitov <ast at kernel.org>
> ---
> security/selinux/hooks.c | 111 ++++++++++++++++++++++++++++++++++++
> security/selinux/include/classmap.h | 2 +
> security/selinux/include/objsec.h | 4 ++
> 3 files changed, 117 insertions(+)
Not sure if DaveM has merged this into net-next yet, but it looks
reasonable to me.
Acked-by: Paul Moore <paul at paul-moore.com>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index f5d304736852..12cf7de8cbed 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -85,6 +85,7 @@
> #include <linux/export.h>
> #include <linux/msg.h>
> #include <linux/shm.h>
> +#include <linux/bpf.h>
>
> #include "avc.h"
> #include "objsec.h"
> @@ -6252,6 +6253,106 @@ static void selinux_ib_free_security(void *ib_sec)
> }
> #endif
>
> +#ifdef CONFIG_BPF_SYSCALL
> +static int selinux_bpf(int cmd, union bpf_attr *attr,
> + unsigned int size)
> +{
> + u32 sid = current_sid();
> + int ret;
> +
> + switch (cmd) {
> + case BPF_MAP_CREATE:
> + ret = avc_has_perm(sid, sid, SECCLASS_BPF, BPF__MAP_CREATE,
> + NULL);
> + break;
> + case BPF_PROG_LOAD:
> + ret = avc_has_perm(sid, sid, SECCLASS_BPF, BPF__PROG_LOAD,
> + NULL);
> + break;
> + default:
> + ret = 0;
> + break;
> + }
> +
> + return ret;
> +}
> +
> +static u32 bpf_map_fmode_to_av(fmode_t fmode)
> +{
> + u32 av = 0;
> +
> + if (fmode & FMODE_READ)
> + av |= BPF__MAP_READ;
> + if (fmode & FMODE_WRITE)
> + av |= BPF__MAP_WRITE;
> + return av;
> +}
> +
> +static int selinux_bpf_map(struct bpf_map *map, fmode_t fmode)
> +{
> + u32 sid = current_sid();
> + struct bpf_security_struct *bpfsec;
> +
> + bpfsec = map->security;
> + return avc_has_perm(sid, bpfsec->sid, SECCLASS_BPF,
> + bpf_map_fmode_to_av(fmode), NULL);
> +}
> +
> +static int selinux_bpf_prog(struct bpf_prog *prog)
> +{
> + u32 sid = current_sid();
> + struct bpf_security_struct *bpfsec;
> +
> + bpfsec = prog->aux->security;
> + return avc_has_perm(sid, bpfsec->sid, SECCLASS_BPF,
> + BPF__PROG_RUN, NULL);
> +}
> +
> +static int selinux_bpf_map_alloc(struct bpf_map *map)
> +{
> + struct bpf_security_struct *bpfsec;
> +
> + bpfsec = kzalloc(sizeof(*bpfsec), GFP_KERNEL);
> + if (!bpfsec)
> + return -ENOMEM;
> +
> + 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_alloc(struct bpf_prog_aux *aux)
> +{
> + struct bpf_security_struct *bpfsec;
> +
> + bpfsec = kzalloc(sizeof(*bpfsec), GFP_KERNEL);
> + if (!bpfsec)
> + return -ENOMEM;
> +
> + bpfsec->sid = current_sid();
> + aux->security = bpfsec;
> +
> + return 0;
> +}
> +
> +static void selinux_bpf_prog_free(struct bpf_prog_aux *aux)
> +{
> + struct bpf_security_struct *bpfsec = aux->security;
> +
> + aux->security = NULL;
> + kfree(bpfsec);
> +}
> +#endif
> +
> static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(binder_set_context_mgr, selinux_binder_set_context_mgr),
> LSM_HOOK_INIT(binder_transaction, selinux_binder_transaction),
> @@ -6471,6 +6572,16 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(audit_rule_match, selinux_audit_rule_match),
> LSM_HOOK_INIT(audit_rule_free, selinux_audit_rule_free),
> #endif
> +
> +#ifdef CONFIG_BPF_SYSCALL
> + 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_alloc_security, selinux_bpf_map_alloc),
> + LSM_HOOK_INIT(bpf_prog_alloc_security, selinux_bpf_prog_alloc),
> + LSM_HOOK_INIT(bpf_map_free_security, selinux_bpf_map_free),
> + LSM_HOOK_INIT(bpf_prog_free_security, selinux_bpf_prog_free),
> +#endif
> };
>
> static __init int selinux_init(void)
> diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
> index 35ffb29a69cb..0a7023b5f000 100644
> --- a/security/selinux/include/classmap.h
> +++ b/security/selinux/include/classmap.h
> @@ -237,6 +237,8 @@ struct security_class_mapping secclass_map[] = {
> { "access", NULL } },
> { "infiniband_endport",
> { "manage_subnet", NULL } },
> + { "bpf",
> + {"map_create", "map_read", "map_write", "prog_load", "prog_run"} },
> { NULL }
> };
>
> diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h
> index 1649cd18eb0b..3d54468ce334 100644
> --- a/security/selinux/include/objsec.h
> +++ b/security/selinux/include/objsec.h
> @@ -150,6 +150,10 @@ struct pkey_security_struct {
> u32 sid; /* SID of pkey */
> };
>
> +struct bpf_security_struct {
> + u32 sid; /*SID of bpf obj creater*/
> +};
> +
> extern unsigned int selinux_checkreqprot;
>
> #endif /* _SELINUX_OBJSEC_H_ */
> --
> 2.15.0.rc1.287.g2b38de12cc-goog
>
--
paul moore
www.paul-moore.com
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