[net-next] bpf: avoid the multi checking

[xiangxia.m.yue@gmail.com]

From: Tonghao Zhang <xiangxia.m.yue@gmail.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@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Song Liu <song@kernel.org>
Cc: Yonghong Song <yhs@fb.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Stanislav Fomichev <sdf@google.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.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