linux-kernel - [PATCH 2/2] bpf: Fix warning of incorrect type in return expression

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Message-ID: <YxOkt4An+u1azlvG@playground>
Date:   Sat, 3 Sep 2022 20:02:15 +0100
From:   Jules Irenge <jbi.octave@...il.com>
To:     martin.lau@...ux.dev
Cc:     Elana.Copperman@...ileye.com, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, song@...nel.org, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org, sdf@...gle.com,
        haoluo@...gle.com
Subject: [PATCH 2/2] bpf: Fix warning of incorrect type in return expression

Sparse reports a warning at bpf_array_map_seq_start()

"warning: incorrect type in return expression (different address spaces)"

The root cause is the function expect a return of type void *
but instead got a percpu value in one of the return.

To fix this a variable of type void * is created
and the complainining return value is saved into the variable and return.

Fix incorrect type in return expression

Signed-off-by: Jules Irenge <jbi.octave@...il.com>
---
 kernel/bpf/arraymap.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 624527401d4d..b1914168c23a 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -548,6 +548,7 @@ static void *bpf_array_map_seq_start(struct seq_file *seq, loff_t *pos)
 	struct bpf_map *map = info->map;
 	struct bpf_array *array;
 	u32 index;
+	void *pptrs;
 
 	if (info->index >= map->max_entries)
 		return NULL;
@@ -556,8 +557,10 @@ static void *bpf_array_map_seq_start(struct seq_file *seq, loff_t *pos)
 		++*pos;
 	array = container_of(map, struct bpf_array, map);
 	index = info->index & array->index_mask;
-	if (info->percpu_value_buf)
-	       return array->pptrs[index];
+	if (info->percpu_value_buf) {
+		pptrs = &array->pptrs[index];
+		return pptrs;
+	}
 	return array_map_elem_ptr(array, index);
 }
 
-- 
2.35.1