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bpf,lsm: Refactor bpf_map_alloc/bpf_map_free LSM hooks

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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
This commit is contained in:
Andrii Nakryiko 2024-01-23 18:21:07 -08:00 committed by Alexei Starovoitov
parent 1b67772e4e
commit a2431c7eab
6 changed files with 26 additions and 18 deletions
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5
include/linux/lsm_hook_defs.h
View file

@ -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)

6
include/linux/security.h
View file

@ -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;
}

6
kernel/bpf/bpf_lsm.c
View file

@ -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)

4
kernel/bpf/syscall.c
View file

@ -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)

16
security/security.c
View file

@ -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);
}
/**

7
security/selinux/hooks.c
View file

@ -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