bpf,lsm: refactor bpf_map_alloc/bpf_map_free LSM hooks

Similarly to bpf_prog_alloc LSM hook, rename and extend bpf_map_alloc
hook into bpf_map_create, taking not just struct bpf_map, but also
bpf_attr and bpf_token, to give a fuller context to LSMs.

Unlike bpf_prog_alloc, there is no need to move the hook around, as it
currently is firing right before allocating BPF map ID and FD, which
seems to be a sweet spot.

But like bpf_prog_alloc/bpf_prog_free combo, make sure that bpf_map_free
LSM hook is called even if bpf_map_create hook returned error, as if few
LSMs are combined together it could be that one LSM successfully
allocated security blob for its needs, while subsequent LSM rejected BPF
map creation. The former LSM would still need to free up LSM blob, so we
need to ensure security_bpf_map_free() is called regardless of the
outcome.

Acked-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231130185229.2688956-11-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 14 insertions, 9 deletions

diff --git a/security/security.c b/security/security.c
index c8a1c66cfaad..ad24cf36da94 100644
--- a/security/security.c
+++ b/security/security.c
@@ -5167,16 +5167,20 @@ int security_bpf_prog(struct bpf_prog *prog)
 }
 
 /**
- * security_bpf_map_alloc() - Allocate a bpf map LSM blob
- * @map: bpf map
+ * security_bpf_map_create() - Check if BPF map creation is allowed
+ * @map: BPF map object
+ * @attr: BPF syscall attributes used to create BPF map
+ * @token: BPF token used to grant user access
  *
- * Initialize the security field inside bpf map.
+ * Do a check when the kernel creates a new BPF map. This is also the
+ * point where LSM blob is allocated for LSMs that need them.
  *
  * Return: Returns 0 on success, error on failure.
  */
-int security_bpf_map_alloc(struct bpf_map *map)
+int security_bpf_map_create(struct bpf_map *map, union bpf_attr *attr,
+			    struct bpf_token *token)
 {
-	return call_int_hook(bpf_map_alloc_security, 0, map);
+	return call_int_hook(bpf_map_create, 0, map, attr, token);
 }
 
 /**
@@ -5205,7 +5209,7 @@ int security_bpf_prog_load(struct bpf_prog *prog, union bpf_attr *attr,
  */
 void security_bpf_map_free(struct bpf_map *map)
 {
-	call_void_hook(bpf_map_free_security, map);
+	call_void_hook(bpf_map_free, map);
 }
 
 /**
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index eabee39e983c..002351ab67b7 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6783,7 +6783,8 @@ static int selinux_bpf_prog(struct bpf_prog *prog)
 			    BPF__PROG_RUN, NULL);
 }
 
-static int selinux_bpf_map_alloc(struct bpf_map *map)
+static int selinux_bpf_map_create(struct bpf_map *map, union bpf_attr *attr,
+				  struct bpf_token *token)
 {
 	struct bpf_security_struct *bpfsec;
 
@@ -7180,7 +7181,7 @@ 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_security, selinux_bpf_map_free),
+	LSM_HOOK_INIT(bpf_map_free, selinux_bpf_map_free),
 	LSM_HOOK_INIT(bpf_prog_free, selinux_bpf_prog_free),
 #endif
 
@@ -7238,7 +7239,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
 	LSM_HOOK_INIT(audit_rule_init, selinux_audit_rule_init),
 #endif
 #ifdef CONFIG_BPF_SYSCALL
-	LSM_HOOK_INIT(bpf_map_alloc_security, selinux_bpf_map_alloc),
+	LSM_HOOK_INIT(bpf_map_create, selinux_bpf_map_create),
 	LSM_HOOK_INIT(bpf_prog_load, selinux_bpf_prog_load),
 #endif
 #ifdef CONFIG_PERF_EVENTS