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Message-Id: <20250125-bpf_dynptr_probe-v1-2-c3cb121f6951@outlook.com>
Date: Sat, 25 Jan 2025 16:23:37 +0800
From: Levi Zim via B4 Relay <devnull+rsworktech.outlook.com@...nel.org>
To: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
Yonghong Song <yonghong.song@...ux.dev>,
John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>, Matt Bobrowski <mattbobrowski@...gle.com>,
Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
Andrii Nakryiko <andrii.nakryiko@...il.com>,
Levi Zim <rsworktech@...look.com>
Subject: [PATCH 2/7] bpf: Implement bpf_probe_read_user_dynptr helper
From: Levi Zim <rsworktech@...look.com>
This patch add a helper function bpf_probe_read_user_dynptr:
long bpf_probe_read_user_dynptr(const struct bpf_dynptr *dst,
u32 offset, u32 size, const void *unsafe_ptr, u64 flags);
It is useful for reading variable-length data from user memory into
dynptr.
Signed-off-by: Levi Zim <rsworktech@...look.com>
---
include/uapi/linux/bpf.h | 16 ++++++++++
kernel/bpf/helpers.c | 3 ++
kernel/trace/bpf_trace.c | 76 +++++++++++++++++++++++++++++++++---------------
3 files changed, 71 insertions(+), 24 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 2e08a59527ecf56732ea14ac34446b5eb25b5690..d7d7a9ddd5dca07ba89d81ba77101a704af3163b 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5820,6 +5820,21 @@ union bpf_attr {
* support this helper, or if *flags* is not 0.
*
* Or other negative errors on failure reading kernel memory.
+ *
+ * long bpf_probe_read_user_dynptr(const struct bpf_dynptr *dst, u32 offset, u32 size, const void *unsafe_ptr, u64 flags)
+ * Description
+ * Safely attempt to read *size* bytes from user space address
+ * *unsafe_ptr* and store the data in *dst* starting from *offset*.
+ * *flags* is currently unused.
+ * Return
+ * 0 on success.
+ *
+ * **-E2BIG** if *offset* + *len* exceeds the length of *src*'s data
+ *
+ * **-EINVAL** if *src* is an invalid dynptr or doesn't support this
+ * support this helper, or if *flags* is not 0.
+ *
+ * Or other negative errors on failure reading user space memory.
*/
#define ___BPF_FUNC_MAPPER(FN, ctx...) \
FN(unspec, 0, ##ctx) \
@@ -6035,6 +6050,7 @@ union bpf_attr {
FN(cgrp_storage_get, 210, ##ctx) \
FN(cgrp_storage_delete, 211, ##ctx) \
FN(probe_read_kernel_dynptr, 212, ##ctx) \
+ FN(probe_read_user_dynptr, 213, ##ctx) \
/* */
/* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index a736dc9e7be98571103ba404420be0da4dac4fbe..ac563d09082e7c721999d7de035aabc000206a29 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1898,6 +1898,7 @@ const struct bpf_func_proto bpf_get_current_task_proto __weak;
const struct bpf_func_proto bpf_get_current_task_btf_proto __weak;
const struct bpf_func_proto bpf_probe_read_user_proto __weak;
const struct bpf_func_proto bpf_probe_read_user_str_proto __weak;
+const struct bpf_func_proto bpf_probe_read_user_dynptr_proto __weak;
const struct bpf_func_proto bpf_probe_read_kernel_proto __weak;
const struct bpf_func_proto bpf_probe_read_kernel_str_proto __weak;
const struct bpf_func_proto bpf_probe_read_kernel_dynptr_proto __weak;
@@ -2029,6 +2030,8 @@ bpf_base_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_get_current_task_btf_proto;
case BPF_FUNC_probe_read_user:
return &bpf_probe_read_user_proto;
+ case BPF_FUNC_probe_read_user_dynptr:
+ return &bpf_probe_read_user_dynptr_proto;
case BPF_FUNC_probe_read_kernel:
return security_locked_down(LOCKDOWN_BPF_READ_KERNEL) < 0 ?
NULL : &bpf_probe_read_kernel_proto;
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 75c9d1e8d04c3b8930ae81345f5586756ce8b5ec..d9f704c1342773c74b2414be4adfc8271d6d364d 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -181,6 +181,36 @@ bpf_probe_read_user_common(void *dst, u32 size, const void __user *unsafe_ptr)
return ret;
}
+static int bpf_probe_read_check_dynptr(const struct bpf_dynptr_kern *dst,
+ u32 offset, u32 size, u64 flags)
+{
+ enum bpf_dynptr_type type;
+ int err;
+
+ if (!dst->data || __bpf_dynptr_is_rdonly(dst))
+ return -EINVAL;
+
+ err = bpf_dynptr_check_off_len(dst, offset, size);
+ if (err)
+ return err;
+
+ type = bpf_dynptr_get_type(dst);
+
+ switch (type) {
+ case BPF_DYNPTR_TYPE_LOCAL:
+ case BPF_DYNPTR_TYPE_RINGBUF:
+ if (flags)
+ return -EINVAL;
+ return 0;
+ case BPF_DYNPTR_TYPE_SKB:
+ case BPF_DYNPTR_TYPE_XDP:
+ return -EINVAL;
+ default:
+ WARN_ONCE(true, "%s: unknown dynptr type %d\n", __func__, type);
+ return -EFAULT;
+ }
+}
+
BPF_CALL_3(bpf_probe_read_user, void *, dst, u32, size,
const void __user *, unsafe_ptr)
{
@@ -196,6 +226,26 @@ const struct bpf_func_proto bpf_probe_read_user_proto = {
.arg3_type = ARG_ANYTHING,
};
+BPF_CALL_5(bpf_probe_read_user_dynptr, const struct bpf_dynptr_kern *, dst,
+ u32, offset, u32, size, void *, unsafe_ptr, u64, flags)
+{
+ int ret = bpf_probe_read_check_dynptr(dst, offset, size, flags);
+
+ return ret ?: bpf_probe_read_user_common(dst->data + dst->offset + offset,
+ size, unsafe_ptr);
+}
+
+const struct bpf_func_proto bpf_probe_read_user_dynptr_proto = {
+ .func = bpf_probe_read_user_dynptr,
+ .gpl_only = true,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_DYNPTR | MEM_RDONLY,
+ .arg2_type = ARG_ANYTHING,
+ .arg3_type = ARG_ANYTHING,
+ .arg4_type = ARG_ANYTHING,
+ .arg5_type = ARG_ANYTHING,
+};
+
static __always_inline int
bpf_probe_read_user_str_common(void *dst, u32 size,
const void __user *unsafe_ptr)
@@ -251,32 +301,10 @@ const struct bpf_func_proto bpf_probe_read_kernel_proto = {
BPF_CALL_5(bpf_probe_read_kernel_dynptr, const struct bpf_dynptr_kern *, dst,
u32, offset, u32, size, void *, unsafe_ptr, u64, flags)
{
- enum bpf_dynptr_type type;
- int err;
-
- if (!dst->data || __bpf_dynptr_is_rdonly(dst))
- return -EINVAL;
+ int ret = bpf_probe_read_check_dynptr(dst, offset, size, flags);
- err = bpf_dynptr_check_off_len(dst, offset, size);
- if (err)
- return err;
-
- type = bpf_dynptr_get_type(dst);
-
- switch (type) {
- case BPF_DYNPTR_TYPE_LOCAL:
- case BPF_DYNPTR_TYPE_RINGBUF:
- if (flags)
- return -EINVAL;
- return bpf_probe_read_kernel_common(dst->data + dst->offset + offset,
+ return ret ?: bpf_probe_read_kernel_common(dst->data + dst->offset + offset,
size, unsafe_ptr);
- case BPF_DYNPTR_TYPE_SKB:
- case BPF_DYNPTR_TYPE_XDP:
- return -EINVAL;
- default:
- WARN_ONCE(true, "%s: unknown dynptr type %d\n", __func__, type);
- return -EFAULT;
- }
}
const struct bpf_func_proto bpf_probe_read_kernel_dynptr_proto = {
--
2.48.1
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