linux-kernel - [PATCH 20/23] bpf: Add bpf_copy_to

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Date:   Wed, 19 May 2021 15:13:31 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     io-uring@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Jens Axboe <axboe@...nel.dk>, 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>,
        KP Singh <kpsingh@...nel.org>,
        Horst Schirmeier <horst.schirmeier@...dortmund.de>,
        "Franz-B . Tuneke" <franz-bernhard.tuneke@...dortmund.de>,
        Christian Dietrich <stettberger@...ucode.de>
Subject: [PATCH 20/23] bpf: Add bpf_copy_to_user() helper

Similarly to bpf_copy_from_user(), also allow sleepable BPF programs
to write to user memory.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 include/linux/bpf.h            |  1 +
 include/uapi/linux/bpf.h       |  8 ++++++++
 kernel/bpf/helpers.c           | 17 +++++++++++++++++
 tools/include/uapi/linux/bpf.h |  7 +++++++
 4 files changed, 33 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 00597b0c719c..9b775e2b2a01 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1899,6 +1899,7 @@ extern const struct bpf_func_proto bpf_skc_to_tcp_timewait_sock_proto;
 extern const struct bpf_func_proto bpf_skc_to_tcp_request_sock_proto;
 extern const struct bpf_func_proto bpf_skc_to_udp6_sock_proto;
 extern const struct bpf_func_proto bpf_copy_from_user_proto;
+extern const struct bpf_func_proto bpf_copy_to_user_proto;
 extern const struct bpf_func_proto bpf_snprintf_btf_proto;
 extern const struct bpf_func_proto bpf_per_cpu_ptr_proto;
 extern const struct bpf_func_proto bpf_this_cpu_ptr_proto;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 7719ec4a33e7..6f19839d2b05 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3648,6 +3648,13 @@ union bpf_attr {
  * 	Return
  * 		0 on success, or a negative error in case of failure.
  *
+ * long bpf_copy_to_user(void *user_ptr, const void *src, u32 size)
+ * 	Description
+ * 		Read *size* bytes from *src* and store the data in user space
+ * 		address *user_ptr*. This is a wrapper of **copy_to_user**\ ().
+ * 	Return
+ * 		0 on success, or a negative error in case of failure.
+ *
  * long bpf_snprintf_btf(char *str, u32 str_size, struct btf_ptr *ptr, u32 btf_ptr_size, u64 flags)
  *	Description
  *		Use BTF to store a string representation of *ptr*->ptr in *str*,
@@ -4085,6 +4092,7 @@ union bpf_attr {
 	FN(iouring_queue_sqe),		\
 	FN(iouring_emit_cqe),		\
 	FN(iouring_reap_cqe),		\
+	FN(copy_to_user),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 308427fe03a3..9d7814c564e5 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -634,6 +634,23 @@ const struct bpf_func_proto bpf_copy_from_user_proto = {
 	.arg3_type	= ARG_ANYTHING,
 };
 
+BPF_CALL_3(bpf_copy_to_user, void __user *, user_ptr,
+	   const void *, src, u32, size)
+{
+	int ret = copy_to_user(user_ptr, src, size);
+
+	return ret ? -EFAULT : 0;
+}
+
+const struct bpf_func_proto bpf_copy_to_user_proto = {
+	.func		= bpf_copy_to_user,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_ANYTHING,
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
+};
+
 BPF_CALL_2(bpf_per_cpu_ptr, const void *, ptr, u32, cpu)
 {
 	if (cpu >= nr_cpu_ids)
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 79c893310492..18d497247d69 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3647,6 +3647,13 @@ union bpf_attr {
  * 	Return
  * 		0 on success, or a negative error in case of failure.
  *
+ * long bpf_copy_to_user(void *user_ptr, const void *src, u32 size)
+ * 	Description
+ * 		Read *size* bytes from *src* and store the data in user space
+ * 		address *user_ptr*. This is a wrapper of **copy_to_user**\ ().
+ * 	Return
+ * 		0 on success, or a negative error in case of failure.
+ *
  * long bpf_snprintf_btf(char *str, u32 str_size, struct btf_ptr *ptr, u32 btf_ptr_size, u64 flags)
  *	Description
  *		Use BTF to store a string representation of *ptr*->ptr in *str*,
-- 
2.31.1