Add the bpf_lookup_user_key() and bpf_key_put() helpers, to respectively search a key with a given serial and flags, and release the reference count of the found key.
Signed-off-by: Roberto Sassu roberto.sassu@huawei.com --- include/uapi/linux/bpf.h | 25 ++++++++++++++++ kernel/bpf/bpf_lsm.c | 53 ++++++++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 6 ++-- scripts/bpf_doc.py | 2 ++ tools/include/uapi/linux/bpf.h | 25 ++++++++++++++++ 5 files changed, 109 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 379e68fb866f..a3f6506ddeba 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -5327,6 +5327,29 @@ union bpf_attr { * **-EACCES** if the SYN cookie is not valid. * * **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin. + * + * struct key *bpf_lookup_user_key(u32 serial, u64 flags) + * Description + * Search a key with a given *serial* and the provided *flags*. The + * returned key, if found, has the reference count incremented by + * one, and must be passed to bpf_key_put() when done with it. + * Permission checks are deferred to the time the key is used by + * one of the available key-specific helpers. + * + * Set *flags* with 1 to attempt creating a requested special + * keyring (e.g. session keyring), if it doesn't yet exist. Set + * *flags* to 2 to lookup a key without waiting for the key + * construction, and to retrieve uninstantiated keys (keys without + * data attached to them). + * Return + * A key pointer if the key is found, a NULL pointer otherwise. + * + * void bpf_key_put(struct key *key) + * Description + * Decrement the reference count of *key* obtained with the + * bpf_lookup_user_key() helper. + * Return + * 0 */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5537,6 +5560,8 @@ union bpf_attr { FN(tcp_raw_gen_syncookie_ipv6), \ FN(tcp_raw_check_syncookie_ipv4), \ FN(tcp_raw_check_syncookie_ipv6), \ + FN(lookup_user_key), \ + FN(key_put), \ /* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c index d469b7f3deef..0a95e2137d65 100644 --- a/kernel/bpf/bpf_lsm.c +++ b/kernel/bpf/bpf_lsm.c @@ -184,6 +184,51 @@ static const struct bpf_func_proto bpf_get_attach_cookie_proto = { .arg1_type = ARG_PTR_TO_CTX, };
+#ifdef CONFIG_KEYS +BTF_ID_LIST_SINGLE(btf_key_ids, struct, key) + +BPF_CALL_2(bpf_lookup_user_key, u32, serial, u64, flags) +{ + key_ref_t key_ref; + + /* Keep in sync with include/linux/key.h. */ + if (flags > (KEY_LOOKUP_PARTIAL << 1) - 1) + return (unsigned long)NULL; + + /* Permission check is deferred until actual helper using the key. */ + key_ref = lookup_user_key(serial, flags, KEY_DEFER_PERM_CHECK); + if (IS_ERR(key_ref)) + return (unsigned long)NULL; + + return (unsigned long)key_ref_to_ptr(key_ref); +} + +static const struct bpf_func_proto bpf_lookup_user_key_proto = { + .func = bpf_lookup_user_key, + .gpl_only = false, + .ret_type = RET_PTR_TO_BTF_ID_OR_NULL, + .ret_btf_id = &btf_key_ids[0], + .arg1_type = ARG_ANYTHING, + .arg2_type = ARG_ANYTHING, + .allowed = bpf_ima_inode_hash_allowed, +}; + +BPF_CALL_1(bpf_key_put, struct key *, key) +{ + key_put(key); + return 0; +} + +static const struct bpf_func_proto bpf_key_put_proto = { + .func = bpf_key_put, + .gpl_only = false, + .ret_type = RET_VOID, + .arg1_type = ARG_PTR_TO_BTF_ID | OBJ_RELEASE, + .arg1_btf_id = &btf_key_ids[0], + .allowed = bpf_ima_inode_hash_allowed, +}; +#endif /* CONFIG_KEYS */ + static const struct bpf_func_proto * bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) { @@ -239,6 +284,14 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) prog->aux->attach_btf_id)) return &bpf_unlocked_sk_getsockopt_proto; return NULL; +#ifdef CONFIG_KEYS + case BPF_FUNC_lookup_user_key: + return prog->aux->sleepable ? + &bpf_lookup_user_key_proto : NULL; + case BPF_FUNC_key_put: + return prog->aux->sleepable ? + &bpf_key_put_proto : NULL; +#endif /* CONFIG_KEYS */ default: return tracing_prog_func_proto(func_id, prog); } diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 328cfab3af60..d9f52fbfb660 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -483,7 +483,8 @@ static bool may_be_acquire_function(enum bpf_func_id func_id) func_id == BPF_FUNC_sk_lookup_udp || func_id == BPF_FUNC_skc_lookup_tcp || func_id == BPF_FUNC_map_lookup_elem || - func_id == BPF_FUNC_ringbuf_reserve; + func_id == BPF_FUNC_ringbuf_reserve || + func_id == BPF_FUNC_lookup_user_key; }
static bool is_acquire_function(enum bpf_func_id func_id, @@ -495,7 +496,8 @@ static bool is_acquire_function(enum bpf_func_id func_id, func_id == BPF_FUNC_sk_lookup_udp || func_id == BPF_FUNC_skc_lookup_tcp || func_id == BPF_FUNC_ringbuf_reserve || - func_id == BPF_FUNC_kptr_xchg) + func_id == BPF_FUNC_kptr_xchg || + func_id == BPF_FUNC_lookup_user_key) return true;
if (func_id == BPF_FUNC_map_lookup_elem && diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py index a0ec321469bd..3d5a7ad6f493 100755 --- a/scripts/bpf_doc.py +++ b/scripts/bpf_doc.py @@ -637,6 +637,7 @@ class PrinterHelpers(Printer): 'struct bpf_dynptr', 'struct iphdr', 'struct ipv6hdr', + 'struct key', ] known_types = { '...', @@ -690,6 +691,7 @@ class PrinterHelpers(Printer): 'struct bpf_dynptr', 'struct iphdr', 'struct ipv6hdr', + 'struct key', } mapped_types = { 'u8': '__u8', diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 379e68fb866f..a3f6506ddeba 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -5327,6 +5327,29 @@ union bpf_attr { * **-EACCES** if the SYN cookie is not valid. * * **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin. + * + * struct key *bpf_lookup_user_key(u32 serial, u64 flags) + * Description + * Search a key with a given *serial* and the provided *flags*. The + * returned key, if found, has the reference count incremented by + * one, and must be passed to bpf_key_put() when done with it. + * Permission checks are deferred to the time the key is used by + * one of the available key-specific helpers. + * + * Set *flags* with 1 to attempt creating a requested special + * keyring (e.g. session keyring), if it doesn't yet exist. Set + * *flags* to 2 to lookup a key without waiting for the key + * construction, and to retrieve uninstantiated keys (keys without + * data attached to them). + * Return + * A key pointer if the key is found, a NULL pointer otherwise. + * + * void bpf_key_put(struct key *key) + * Description + * Decrement the reference count of *key* obtained with the + * bpf_lookup_user_key() helper. + * Return + * 0 */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5537,6 +5560,8 @@ union bpf_attr { FN(tcp_raw_gen_syncookie_ipv6), \ FN(tcp_raw_check_syncookie_ipv4), \ FN(tcp_raw_check_syncookie_ipv6), \ + FN(lookup_user_key), \ + FN(key_put), \ /* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper