netdev - [net-next] bpf: avoid the multi checking

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Message-Id: <20221121100521.56601-1-xiangxia.m.yue@gmail.com>
Date:   Mon, 21 Nov 2022 18:05:20 +0800
From:   xiangxia.m.yue@...il.com
To:     unlisted-recipients:; (no To-header on input)
Cc:     netdev@...r.kernel.org, Tonghao Zhang <xiangxia.m.yue@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>
Subject: [net-next] bpf: avoid the multi checking

From: Tonghao Zhang <xiangxia.m.yue@...il.com>

.map_alloc_check checked bpf_attr::max_entries, and if bpf_attr::max_entries
== 0, return -EINVAL. bpf_htab::n_buckets will not be 0, while -E2BIG is not
appropriate.

Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Andrii Nakryiko <andrii@...nel.org>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: Song Liu <song@...nel.org>
Cc: Yonghong Song <yhs@...com>
Cc: John Fastabend <john.fastabend@...il.com>
Cc: KP Singh <kpsingh@...nel.org>
Cc: Stanislav Fomichev <sdf@...gle.com>
Cc: Hao Luo <haoluo@...gle.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@...il.com>
---
 kernel/bpf/hashtab.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 50d254cd0709..22855d6ff6d3 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -500,9 +500,10 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
 		htab->elem_size += round_up(htab->map.value_size, 8);
 
 	err = -E2BIG;
-	/* prevent zero size kmalloc and check for u32 overflow */
-	if (htab->n_buckets == 0 ||
-	    htab->n_buckets > U32_MAX / sizeof(struct bucket))
+	/* avoid zero size and u32 overflow kmalloc.
+	 * bpf_attr::max_entries checked in .map_alloc_check().
+	 */
+	if (htab->n_buckets > U32_MAX / sizeof(struct bucket))
 		goto free_htab;
 
 	err = -ENOMEM;
-- 
2.27.0