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.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/bpf/20240124022127.2379740-11-andrii@kernel.org

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 370181aa685b2ea64a64bc57ec57365e815d11f7..1be4d3ca6efb2deec6e6de976193ddd120fe0956 100644 (file)
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -404,8 +404,9 @@ LSM_HOOK(void, LSM_RET_VOID, audit_rule_free, void *lsmrule)
 LSM_HOOK(int, 0, bpf, int cmd, union bpf_attr *attr, unsigned int size)
 LSM_HOOK(int, 0, bpf_map, struct bpf_map *map, fmode_t fmode)
 LSM_HOOK(int, 0, bpf_prog, struct bpf_prog *prog)
-LSM_HOOK(int, 0, bpf_map_alloc_security, struct bpf_map *map)
-LSM_HOOK(void, LSM_RET_VOID, bpf_map_free_security, struct bpf_map *map)
+LSM_HOOK(int, 0, bpf_map_create, struct bpf_map *map, union bpf_attr *attr,
+        struct bpf_token *token)
+LSM_HOOK(void, LSM_RET_VOID, bpf_map_free, struct bpf_map *map)
 LSM_HOOK(int, 0, bpf_prog_load, struct bpf_prog *prog, union bpf_attr *attr,
         struct bpf_token *token)
 LSM_HOOK(void, LSM_RET_VOID, bpf_prog_free, struct bpf_prog *prog)

diff --git a/include/linux/security.h b/include/linux/security.h
index cb2932fce448dbb197332cf0f5ea79146970138a..83fcdc97411666cb710cbc26c27c92fd93667f5a 100644 (file)
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -2069,7 +2069,8 @@ struct bpf_token;
 extern int security_bpf(int cmd, union bpf_attr *attr, unsigned int size);
 extern int security_bpf_map(struct bpf_map *map, fmode_t fmode);
 extern int security_bpf_prog(struct bpf_prog *prog);
-extern int security_bpf_map_alloc(struct bpf_map *map);
+extern int security_bpf_map_create(struct bpf_map *map, union bpf_attr *attr,
+                                  struct bpf_token *token);
 extern void security_bpf_map_free(struct bpf_map *map);
 extern int security_bpf_prog_load(struct bpf_prog *prog, union bpf_attr *attr,
                                  struct bpf_token *token);
@@ -2091,7 +2092,8 @@ static inline int security_bpf_prog(struct bpf_prog *prog)
        return 0;
 }
 
-static inline int security_bpf_map_alloc(struct bpf_map *map)
+static inline int security_bpf_map_create(struct bpf_map *map, union bpf_attr *attr,
+                                         struct bpf_token *token)
 {
        return 0;
 }

diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 7ee0dd011de47514e9ce32f46890bfac5deaa375..76976908b302ee6ad8a8a3a837426cefda287fe0 100644 (file)
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -260,8 +260,8 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 BTF_SET_START(sleepable_lsm_hooks)
 BTF_ID(func, bpf_lsm_bpf)
 BTF_ID(func, bpf_lsm_bpf_map)
-BTF_ID(func, bpf_lsm_bpf_map_alloc_security)
-BTF_ID(func, bpf_lsm_bpf_map_free_security)
+BTF_ID(func, bpf_lsm_bpf_map_create)
+BTF_ID(func, bpf_lsm_bpf_map_free)
 BTF_ID(func, bpf_lsm_bpf_prog)
 BTF_ID(func, bpf_lsm_bpf_prog_load)
 BTF_ID(func, bpf_lsm_bpf_prog_free)
@@ -359,7 +359,7 @@ BTF_ID(func, bpf_lsm_userns_create)
 BTF_SET_END(sleepable_lsm_hooks)
 
 BTF_SET_START(untrusted_lsm_hooks)
-BTF_ID(func, bpf_lsm_bpf_map_free_security)
+BTF_ID(func, bpf_lsm_bpf_map_free)
 BTF_ID(func, bpf_lsm_bpf_prog_free)
 BTF_ID(func, bpf_lsm_file_alloc_security)
 BTF_ID(func, bpf_lsm_file_free_security)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 3857a2a9ae7f67dff09fc0d413496cb3a74e397e..b2750b79ac8050c448533a23aed14a9c2aa1939b 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1318,9 +1318,9 @@ static int map_create(union bpf_attr *attr)
                        attr->btf_vmlinux_value_type_id;
        }
 
-       err = security_bpf_map_alloc(map);
+       err = security_bpf_map_create(map, attr, token);
        if (err)
-               goto free_map;
+               goto free_map_sec;
 
        err = bpf_map_alloc_id(map);
        if (err)

diff --git a/security/security.c b/security/security.c
index eb159da4b146be548b99474facf0d293e791afdf..26fcab35b6cd280f9631b7ec288e14c7651bbbdc 100644 (file)
--- a/security/security.c
+++ b/security/security.c
@@ -5410,16 +5410,20 @@ 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);
 }
 
 /**
@@ -5448,7 +5452,7 @@ 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 6d64fb189b1b502238e69050bf1508b298eb5327..3d336a7952f79b464d76fdfb7948ea2cdce7b458 100644 (file)
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6920,7 +6920,8 @@ 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;
 
@@ -7325,7 +7326,7 @@ 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
 
@@ -7383,7 +7384,7 @@ 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