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bpf: Reduce smap->elem_size

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'struct bpf_local_storage_elem' has an unused 56 byte padding at the
end due to struct's cache-line alignment requirement. This padding
space is overlapped by storage value contents, so if we use sizeof()
to calculate the total size, we overinflate it by 56 bytes. Use
offsetof() instead to calculate more exact memory use.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221221013036.3427431-1-martin.lau@linux.dev
This commit is contained in:
Martin KaFai Lau 2022-12-20 17:30:36 -08:00 committed by Daniel Borkmann
parent 7b43df6c6e
commit 552d42a356
1 changed files with 2 additions and 2 deletions
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4
kernel/bpf/bpf_local_storage.c
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@ -580,8 +580,8 @@ static struct bpf_local_storage_map *__bpf_local_storage_map_alloc(union bpf_att
raw_spin_lock_init(&smap->buckets[i].lock);
}
smap->elem_size =
sizeof(struct bpf_local_storage_elem) + attr->value_size;
smap->elem_size = offsetof(struct bpf_local_storage_elem,
sdata.data[attr->value_size]);
return smap;
}