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bpf: Drop redundant hash_buf from map_get_hash operation

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bpf_map_get_info_by_fd() is the only caller of the ->map_get_hash
and always invokes it with hash_buf == map->sha and hash_buf_size
of SHA256_DIGEST_SIZE. array_map_get_hash() in turn lets sha256()
write the digest directly into that buffer (map->sha) and then
performs a trailing memcpy(), which evaluates to memcpy(map->sha,
map->sha, 32): a redundant self-copy. The hash_buf_size argument
was never used at all. Simplify this a bit, no functional change.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260601150248.394863-3-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Borkmann 2026-06-01 17:02:43 +02:00 committed by Alexei Starovoitov
parent 9a3c3c49c3
commit c48c3a7e7d
3 changed files with 6 additions and 10 deletions
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2
include/linux/bpf.h
View File

@ -111,7 +111,7 @@ struct bpf_map_ops {
long (*map_pop_elem)(struct bpf_map *map, void *value);
long (*map_peek_elem)(struct bpf_map *map, void *value);
void *(*map_lookup_percpu_elem)(struct bpf_map *map, void *key, u32 cpu);
int (*map_get_hash)(struct bpf_map *map, u32 hash_buf_size, void *hash_buf);
int (*map_get_hash)(struct bpf_map *map);
/* funcs called by prog_array and perf_event_array map */
void *(*map_fd_get_ptr)(struct bpf_map *map, struct file *map_file,

6
kernel/bpf/arraymap.c
View File

@ -175,14 +175,12 @@ static void *array_map_lookup_elem(struct bpf_map *map, void *key)
return array->value + (u64)array->elem_size * (index & array->index_mask);
}
static int array_map_get_hash(struct bpf_map *map, u32 hash_buf_size,
void *hash_buf)
static int array_map_get_hash(struct bpf_map *map)
{
struct bpf_array *array = container_of(map, struct bpf_array, map);
sha256(array->value, (u64)array->elem_size * array->map.max_entries,
hash_buf);
memcpy(array->map.sha, hash_buf, sizeof(array->map.sha));
array->map.sha);
return 0;
}

8
kernel/bpf/syscall.c
View File

@ -5434,18 +5434,16 @@ static int bpf_map_get_info_by_fd(struct file *file,
if (!map->ops->map_get_hash)
return -EINVAL;
if (info.hash_size != SHA256_DIGEST_SIZE)
if (info.hash_size != sizeof(map->sha))
return -EINVAL;
if (!READ_ONCE(map->frozen))
return -EPERM;
err = map->ops->map_get_hash(map, SHA256_DIGEST_SIZE, map->sha);
err = map->ops->map_get_hash(map);
if (err != 0)
return err;
if (copy_to_user(uhash, map->sha, SHA256_DIGEST_SIZE) != 0)
if (copy_to_user(uhash, map->sha, sizeof(map->sha)) != 0)
return -EFAULT;
} else if (info.hash_size) {
return -EINVAL;