On 11/29/2022 3:23 AM, Mimi Zohar wrote:
> On Thu, 2022-11-24 at 09:17 +0100, Roberto Sassu wrote:
>> On Wed, 2022-11-23 at 20:14 -0500, Mimi Zohar wrote:
>>> Hi Roberto,
>>>
>>> On Wed, 2022-11-23 at 16:47 +0100, Roberto Sassu wrote:
>>>> int security_inode_init_security(struct inode *inode, struct inode *dir,
>>>> const struct qstr *qstr,
>>>> const initxattrs initxattrs, void *fs_data)
>>>> {
>>>> - struct xattr new_xattrs[MAX_LSM_EVM_XATTR + 1];
>>>> - struct xattr *lsm_xattr, *evm_xattr, *xattr;
>>>> - int ret;
>>>> + struct security_hook_list *P;
>>>> + struct xattr *new_xattrs;
>>>> + struct xattr *xattr;
>>>> + int ret = -EOPNOTSUPP, num_filled_xattrs = 0;
>>>>
>>>> if (unlikely(IS_PRIVATE(inode)))
>>>> return 0;
>>>>
>>>> + if (!blob_sizes.lbs_xattr)
>>>> + return 0;
>>>> +
>>>> if (!initxattrs)
>>>> return call_int_hook(inode_init_security, -EOPNOTSUPP, inode,
>>>> - dir, qstr, NULL, NULL, NULL);
>>>> - memset(new_xattrs, 0, sizeof(new_xattrs));
>>>> - lsm_xattr = new_xattrs;
>>>> - ret = call_int_hook(inode_init_security, -EOPNOTSUPP, inode, dir, qstr,
>>>> - &lsm_xattr->name,
>>>> - &lsm_xattr->value,
>>>> - &lsm_xattr->value_len);
>>>> - if (ret)
>>>> + dir, qstr, NULL);
>>>> + /* Allocate +1 for EVM and +1 as terminator. */
>>>> + new_xattrs = kcalloc(blob_sizes.lbs_xattr + 2, sizeof(*new_xattrs),
>>>> + GFP_NOFS);
>>>> + if (!new_xattrs)
>>>> + return -ENOMEM;
>>>> +
>>>> + hlist_for_each_entry(P, &security_hook_heads.inode_init_security,
>>>> + list) {
>>>> + ret = P->hook.inode_init_security(inode, dir, qstr, new_xattrs);
>>>> + if (ret && ret != -EOPNOTSUPP)
>>>> + goto out;
>>>> + if (ret == -EOPNOTSUPP)
>>>> + continue;
>>> In this context, -EOPNOTSUPP originally signified that the filesystem
>>> does not support writing xattrs. Writing any xattr would fail.
>>> Returning -ENODATA for no LSM xattr(s) data would seem to be more
>>> appropriate than -EOPNOTSUPP.
>> Hi Mimi
>>
>> I thought about adding new return values. Currently only -EOPNOTSUPP
>> and -ENOMEM are expected as errors.
>>
>> However, changing the conventions would mean revisiting the LSMs code
>> and ensuring that they follow the new conventions.
>>
>> I would be more in favor of not touching it.
> Casey, Paul, any comment?
I don't see value in adding -ENODATA as a value special to
the infrastructure. What would the infrastructure do differently?
The use of -EOPNOTSUPP isn't consistent throughout, and the amount
of "correctness" you get by returning -ENODATA is really small.
>
>>>> + /*
>>>> + * As the number of xattrs reserved by LSMs is not directly
>>>> + * available, directly use the total number blob_sizes.lbs_xattr
>>>> + * to keep the code simple, while being not the most efficient
>>>> + * way.
>>>> + */
>>>> + ret = security_check_compact_filled_xattrs(new_xattrs,
>>>> + blob_sizes.lbs_xattr,
>>>> + &num_filled_xattrs);
>>>> + if (ret < 0) {
>>>> + ret = -ENOMEM;
>>>> + goto out;
>>>> + }
>>>> + }
>>>> +
>>>> + if (!num_filled_xattrs)
>>>> goto out;
>>>>
>>>> - evm_xattr = lsm_xattr + 1;
>>>> - ret = evm_inode_init_security(inode, lsm_xattr, evm_xattr);
>>>> + ret = evm_inode_init_security(inode, new_xattrs,
>>>> + new_xattrs + num_filled_xattrs);
>>>> if (ret)
>>>> goto out;
>>>> ret = initxattrs(inode, new_xattrs, fs_data);
>>>> out:
>>>> for (xattr = new_xattrs; xattr->value != NULL; xattr++)
>>>> kfree(xattr->value);
>>>> + kfree(new_xattrs);
>>>> return (ret == -EOPNOTSUPP) ? 0 : ret;
>>>> }
>>> b
>
