On Tue, Jan 15, 2019 at 09:08:22PM -0800, Alexei Starovoitov wrote:
[ ... ]
> +/* copy everything but bpf_spin_lock */
> +static inline void copy_map_value(struct bpf_map *map, void *dst, void *src)
> +{
> + if (unlikely(map_value_has_spin_lock(map))) {
> + u32 off = map->spin_lock_off;
> +
> + memcpy(dst, src, off);
> + memcpy(dst + off + sizeof(struct bpf_spin_lock),
> + src + off + sizeof(struct bpf_spin_lock),
> + map->value_size - off - sizeof(struct bpf_spin_lock));
> + } else {
> + memcpy(dst, src, map->value_size);
> + }
> +}
> +
[ ... ]
> +int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t)
> +{
> + const struct btf_member *member;
> + u32 i, off = -ENOENT;
> +
> + if (BTF_INFO_KIND(t->info) != BTF_KIND_STRUCT)
> + return -EINVAL;
> +
> + for_each_member(i, t, member) {
> + const struct btf_type *member_type = btf_type_by_id(btf,
> +
> member->type);
> + if (!btf_type_is_struct(member_type))
may be using "BTF_INFO_KIND(t->info) != BTF_KIND_STRUCT" here also.
> + continue;
> + if (member_type->size != sizeof(struct bpf_spin_lock))
> + continue;
> + if (strcmp(__btf_name_by_offset(btf, member_type->name_off),
> + "bpf_spin_lock"))
> + continue;
> + if (off != -ENOENT)
> + /* only one 'struct bpf_spin_lock' is allowed */
> + return -E2BIG;
> + off = btf_member_bit_offset(t, member);
> + if (off % 8)
> + /* valid C code cannot generate such BTF */
> + return -EINVAL;
> + off /= 8;
> + if (off % __alignof__(struct bpf_spin_lock))
> + /* valid struct bpf_spin_lock will be 4 byte aligned */
> + return -EINVAL;
> + }
> + return off;
> +}
> +
[ ... ]
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index b155cd17c1bd..ebf0a673cb83 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
[ ... ]
> err = security_bpf_map_alloc(map);
> @@ -740,7 +757,7 @@ static int map_lookup_elem(union bpf_attr *attr)
> err = -ENOENT;
> } else {
> err = 0;
> - memcpy(value, ptr, value_size);
> + copy_map_value(map, value, ptr);
copy_map_value() skips the bpf_spin_lock and "value" has not been zero-ed.
"value" is then copied to the "__user *uvalue".
May be init the bpf_spin_lock part of the "uvalue" to 0?
btw, somehow patch 6 and 7 are missing:
https://patchwork.ozlabs.org/cover/1025640/
