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Date: Tue, 12 Jul 2022 20:41:24 +0200
From: Roberto Sassu <roberto.sassu@...wei.com>
To: <ast@...nel.org>, <daniel@...earbox.net>,
<john.fastabend@...il.com>, <andrii@...nel.org>,
<martin.lau@...ux.dev>, <song@...nel.org>, <yhs@...com>,
<kpsingh@...nel.org>, <dhowells@...hat.com>, <jarkko@...nel.org>,
<shuah@...nel.org>
CC: <bpf@...r.kernel.org>, <keyrings@...r.kernel.org>,
<linux-security-module@...r.kernel.org>,
<linux-kselftest@...r.kernel.org>, <netdev@...r.kernel.org>,
<linux-kernel@...r.kernel.org>,
Roberto Sassu <roberto.sassu@...wei.com>
Subject: [PATCH v7 3/7] bpf: Add bpf_lookup_user_key() and bpf_key_put() helpers
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@...wei.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
--
2.25.1
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