linux-kernel - [PATCH for 6.10] bpf: fix order of args in call to bpf_map

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Message-ID: <20240710100521.15061-2-vbabka@suse.cz>
Date: Wed, 10 Jul 2024 12:05:22 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: andrii@...nel.org,
	ast@...nel.org,
	bpf@...r.kernel.org,
	daniel@...earbox.net,
	eddyz87@...il.com,
	haoluo@...gle.com,
	javier.carrasco.cruz@...il.com,
	john.fastabend@...il.com,
	jolsa@...nel.org,
	kent.overstreet@...ux.dev,
	kpsingh@...nel.org,
	linux-kernel@...r.kernel.org,
	lists@...dbynature.de,
	lstoakes@...il.com,
	martin.lau@...ux.dev,
	peter.ujfalusi@...el.com,
	regressions@...ts.linux.dev,
	sdf@...gle.com,
	sheharyaar48@...il.com,
	song@...nel.org,
	surenb@...gle.com,
	vbabka@...e.cz,
	yonghong.song@...ux.dev
Subject: [PATCH for 6.10] bpf: fix order of args in call to bpf_map_kvcalloc

From: Mohammad Shehar Yaar Tausif <sheharyaar48@...il.com>

The original function call passed size of smap->bucket before the number of
buckets which raises the error 'calloc-transposed-args' on compilation.

Vlastimil Babka added:

The order of parameters can be traced back all the way to 6ac99e8f23d4
("bpf: Introduce bpf sk local storage") accross several refactorings,
and that's why the commit is used as a Fixes: tag.

In v6.10-rc1, a different commit 2c321f3f70bc ("mm: change inlined
allocation helpers to account at the call site") however exposed the
order of args in a way that gcc-14 has enough visibility to start
warning about it, because (in !CONFIG_MEMCG case) bpf_map_kvcalloc is
then a macro alias for kvcalloc instead of a static inline wrapper.

To sum up the warning happens when the following conditions are all met:

- gcc-14 is used (didn't see it with gcc-13)
- commit 2c321f3f70bc is present
- CONFIG_MEMCG is not enabled in .config
- CONFIG_WERROR turns this from a compiler warning to error

Fixes: 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage")
Reviewed-by: Andrii Nakryiko <andrii@...nel.org>
Signed-off-by: Mohammad Shehar Yaar Tausif <sheharyaar48@...il.com>
Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 kernel/bpf/bpf_local_storage.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index 976cb258a0ed..c938dea5ddbf 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -782,8 +782,8 @@ bpf_local_storage_map_alloc(union bpf_attr *attr,
 	nbuckets = max_t(u32, 2, nbuckets);
 	smap->bucket_log = ilog2(nbuckets);
 
-	smap->buckets = bpf_map_kvcalloc(&smap->map, sizeof(*smap->buckets),
-					 nbuckets, GFP_USER | __GFP_NOWARN);
+	smap->buckets = bpf_map_kvcalloc(&smap->map, nbuckets,
+					 sizeof(*smap->buckets), GFP_USER | __GFP_NOWARN);
 	if (!smap->buckets) {
 		err = -ENOMEM;
 		goto free_smap;
-- 
2.45.2