From 74523c06ae20b83c5508a98af62393ac34913362 Mon Sep 17 00:00:00 2001
From: Song Liu <song@kernel.org>
Date: Mon, 6 Nov 2023 20:57:23 -0800
Subject: [PATCH] bpf: Add __bpf_dynptr_data* for in kernel use
Different types of bpf dynptr have different internal data storage.
Specifically, SKB and XDP type of dynptr may have non-continuous data.
Therefore, it is not always safe to directly access dynptr->data.
Add __bpf_dynptr_data and __bpf_dynptr_data_rw to replace direct access to
dynptr->data.
Update bpf_verify_pkcs7_signature to use __bpf_dynptr_data instead of
dynptr->data.
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://lore.kernel.org/bpf/20231107045725.2278852-2-song@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
include/linux/bpf.h | 2 ++
kernel/bpf/helpers.c | 19 +++++++++++++++++++
kernel/trace/bpf_trace.c | 12 ++++++++----
3 files changed, 29 insertions(+), 4 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index b4825d3cdb292..eb84caf133df9 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1222,6 +1222,8 @@ enum bpf_dynptr_type {
int bpf_dynptr_check_size(u32 size);
u32 __bpf_dynptr_size(const struct bpf_dynptr_kern *ptr);
+const void *__bpf_dynptr_data(const struct bpf_dynptr_kern *ptr, u32 len);
+void *__bpf_dynptr_data_rw(const struct bpf_dynptr_kern *ptr, u32 len);
#ifdef CONFIG_BPF_JIT
int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr);
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 56b0c1f678ee7..174f02a9e7034 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2618,3 +2618,22 @@ static int __init kfunc_init(void)
}
late_initcall(kfunc_init);
+
+/* Get a pointer to dynptr data up to len bytes for read only access. If
+ * the dynptr doesn't have continuous data up to len bytes, return NULL.
+ */
+const void *__bpf_dynptr_data(const struct bpf_dynptr_kern *ptr, u32 len)
+{
+ return bpf_dynptr_slice(ptr, 0, NULL, len);
+}
+
+/* Get a pointer to dynptr data up to len bytes for read write access. If
+ * the dynptr doesn't have continuous data up to len bytes, or the dynptr
+ * is read only, return NULL.
+ */
+void *__bpf_dynptr_data_rw(const struct bpf_dynptr_kern *ptr, u32 len)
+{
+ if (__bpf_dynptr_is_rdonly(ptr))
+ return NULL;
+ return (void *)__bpf_dynptr_data(ptr, len);
+}
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 84e8a0f6e4e0b..f0b8b7c291262 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1376,6 +1376,8 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
struct bpf_dynptr_kern *sig_ptr,
struct bpf_key *trusted_keyring)
{
+ const void *data, *sig;
+ u32 data_len, sig_len;
int ret;
if (trusted_keyring->has_ref) {
@@ -1392,10 +1394,12 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
return ret;
}
- return verify_pkcs7_signature(data_ptr->data,
- __bpf_dynptr_size(data_ptr),
- sig_ptr->data,
- __bpf_dynptr_size(sig_ptr),
+ data_len = __bpf_dynptr_size(data_ptr);
+ data = __bpf_dynptr_data(data_ptr, data_len);
+ sig_len = __bpf_dynptr_size(sig_ptr);
+ sig = __bpf_dynptr_data(sig_ptr, sig_len);
+
+ return verify_pkcs7_signature(data, data_len, sig, sig_len,
trusted_keyring->key,
VERIFYING_UNSPECIFIED_SIGNATURE, NULL,
NULL);
--
2.30.2