linux-kernel - [PATCH v2 bpf 1/5] bpf: bpf_prog_array_alloc() should return a generic non-rcu pointer

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Message-ID: <20180713194114.2711-1-guro@fb.com>
Date:   Fri, 13 Jul 2018 12:41:10 -0700
From:   Roman Gushchin <guro@...com>
To:     <netdev@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <kernel-team@...com>,
        Roman Gushchin <guro@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH v2 bpf 1/5] bpf: bpf_prog_array_alloc() should return a generic non-rcu pointer

Currently the return type of the bpf_prog_array_alloc() is
struct bpf_prog_array __rcu *, which is not quite correct.
Obviously, the returned pointer is a generic pointer, which
is valid for an indefinite amount of time and it's not shared
with anyone else, so there is no sense in marking it as __rcu.

This change eliminate the following sparse warnings:
kernel/bpf/core.c:1544:31: warning: incorrect type in return expression (different address spaces)
kernel/bpf/core.c:1544:31:    expected struct bpf_prog_array [noderef] <asn:4>*
kernel/bpf/core.c:1544:31:    got void *
kernel/bpf/core.c:1548:17: warning: incorrect type in return expression (different address spaces)
kernel/bpf/core.c:1548:17:    expected struct bpf_prog_array [noderef] <asn:4>*
kernel/bpf/core.c:1548:17:    got struct bpf_prog_array *<noident>
kernel/bpf/core.c:1681:15: warning: incorrect type in assignment (different address spaces)
kernel/bpf/core.c:1681:15:    expected struct bpf_prog_array *array
kernel/bpf/core.c:1681:15:    got struct bpf_prog_array [noderef] <asn:4>*

Fixes: 324bda9e6c5a ("bpf: multi program support for cgroup+bpf")
Signed-off-by: Roman Gushchin <guro@...com>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
---
 include/linux/bpf.h | 2 +-
 kernel/bpf/core.c   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 8827e797ff97..943fb08d8287 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -352,7 +352,7 @@ struct bpf_prog_array {
 	struct bpf_prog *progs[0];
 };
 
-struct bpf_prog_array __rcu *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags);
+struct bpf_prog_array *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags);
 void bpf_prog_array_free(struct bpf_prog_array __rcu *progs);
 int bpf_prog_array_length(struct bpf_prog_array __rcu *progs);
 int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs,
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 1e5625d46414..253aa8e79c7b 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1538,7 +1538,7 @@ static struct {
 	.null_prog = NULL,
 };
 
-struct bpf_prog_array __rcu *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags)
+struct bpf_prog_array *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags)
 {
 	if (prog_cnt)
 		return kzalloc(sizeof(struct bpf_prog_array) +
-- 
2.14.4