Hello Martin KaFai Lau,
Commit 179cde8cef7e ("bpf: btf: Check members of struct/union") from
Apr 18, 2018 (linux-next), leads to the following Smatch static
checker warning:
./kernel/bpf/btf.c:2893 btf_array_check_member()
error: uninitialized symbol 'array_size'.
./kernel/bpf/btf.c
2873 static int btf_array_check_member(struct btf_verifier_env *env,
2874 const struct btf_type *struct_type,
2875 const struct btf_member *member,
2876 const struct btf_type *member_type)
2877 {
2878 u32 struct_bits_off = member->offset;
2879 u32 struct_size, bytes_offset;
2880 u32 array_type_id, array_size;
2881 struct btf *btf = env->btf;
2882
2883 if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
2884 btf_verifier_log_member(env, struct_type, member,
2885 "Member is not byte aligned");
2886 return -EINVAL;
2887 }
2888
2889 array_type_id = member->type;
2890 btf_type_id_size(btf, &array_type_id, &array_size);
Potentially this is a false positive and btf_type_id_size() can't fail. But
we're in a check function so intuitively, it feels like we should check for
errors.
Anyway, just let me know if it's a false positive. These warnings are a one
time thing but it's nice to have the information on lore in case someone is
curious.
2891 struct_size = struct_type->size;
2892 bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
--> 2893 if (struct_size - bytes_offset < array_size) {
2894 btf_verifier_log_member(env, struct_type, member,
2895 "Member exceeds struct_size");
2896 return -EINVAL;
2897 }
2898
2899 return 0;
2900 }
regards,
dan carpenter
