netdev - [PATCH RFC bpf-next v1 1/6] bpf: Refactor bpf_check_mod_kfunc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Sat, 30 Oct 2021 20:16:04 +0530
From:   Kumar Kartikeya Dwivedi <memxor@...il.com>
To:     bpf@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        Maxim Mikityanskiy <maximmi@...dia.com>,
        Florian Westphal <fw@...len.de>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: [PATCH RFC bpf-next v1 1/6] bpf: Refactor bpf_check_mod_kfunc_call

Future commits adding more callbacks will implement the same pattern of
matching module owner of kfunc_btf_id_set, and then operating on data in
the struct.

Since all call sites in the verifier hold a reference to struct module
parameter 'owner', it is safe to release the mutex lock and still
reference the struct pointer. This can be consolidated in a common
helper given the reference is always held for owner module parameter.

Since removal from the list is dependent on module reference dropping to
zero, it is safe to assume it is registered as long the caller holds a
reference.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@...il.com>
---
 kernel/bpf/btf.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index dbc3ad07e21b..be1082270455 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6371,22 +6371,35 @@ void unregister_kfunc_btf_id_set(struct kfunc_btf_id_list *l,
 }
 EXPORT_SYMBOL_GPL(unregister_kfunc_btf_id_set);
 
-bool bpf_check_mod_kfunc_call(struct kfunc_btf_id_list *klist, u32 kfunc_id,
-			      struct module *owner)
+/* Caller must hold reference to module 'owner' */
+struct kfunc_btf_id_set *__get_kfunc_btf_id_set(struct kfunc_btf_id_list *klist,
+						struct module *owner)
 {
-	struct kfunc_btf_id_set *s;
+	struct kfunc_btf_id_set *s, *ret = NULL;
 
 	if (!owner)
-		return false;
+		return NULL;
 	mutex_lock(&klist->mutex);
 	list_for_each_entry(s, &klist->list, list) {
-		if (s->owner == owner && btf_id_set_contains(s->set, kfunc_id)) {
-			mutex_unlock(&klist->mutex);
-			return true;
+		if (s->owner == owner) {
+			ret = s;
+			break;
 		}
 	}
 	mutex_unlock(&klist->mutex);
-	return false;
+	return ret;
+}
+
+bool bpf_check_mod_kfunc_call(struct kfunc_btf_id_list *klist, u32 kfunc_id,
+			      struct module *owner)
+{
+	struct kfunc_btf_id_set *s;
+	bool ret = false;
+
+	s = __get_kfunc_btf_id_set(klist, owner);
+	if (s)
+		ret = btf_id_set_contains(s->set, kfunc_id);
+	return ret;
 }
 
 #endif
-- 
2.33.1