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keys: Provide request_key_rcu()

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Provide a request_key_rcu() function that can be used to request a key
under RCU conditions.  It can only search and check permissions; it cannot
allocate a new key, upcall or wait for an upcall to complete.  It may
return a partially constructed key.

Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells
2019-06-19 16:10:15 +01:00
parent e59428f721
commit 896f1950e5
4 changed files with 66 additions and 0 deletions
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44
security/keys/request_key.c
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@@ -756,3 +756,47 @@ struct key *request_key_async_with_auxdata(struct key_type *type,
callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
}
EXPORT_SYMBOL(request_key_async_with_auxdata);
/**
* request_key_rcu - Request key from RCU-read-locked context
* @type: The type of key we want.
* @description: The name of the key we want.
*
* Request a key from a context that we may not sleep in (such as RCU-mode
* pathwalk). Keys under construction are ignored.
*
* Return a pointer to the found key if successful, -ENOKEY if we couldn't find
* a key or some other error if the key found was unsuitable or inaccessible.
*/
struct key *request_key_rcu(struct key_type *type, const char *description)
{
struct keyring_search_context ctx = {
.index_key.type = type,
.index_key.description = description,
.index_key.desc_len = strlen(description),
.cred = current_cred(),
.match_data.cmp = key_default_cmp,
.match_data.raw_data = description,
.match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
.flags = (KEYRING_SEARCH_DO_STATE_CHECK |
KEYRING_SEARCH_SKIP_EXPIRED),
};
struct key *key;
key_ref_t key_ref;
kenter("%s,%s", type->name, description);
/* search all the process keyrings for a key */
key_ref = search_process_keyrings_rcu(&ctx);
if (IS_ERR(key_ref)) {
key = ERR_CAST(key_ref);
if (PTR_ERR(key_ref) == -EAGAIN)
key = ERR_PTR(-ENOKEY);
} else {
key = key_ref_to_ptr(key_ref);
}
kleave(" = %p", key);
return key;
}
EXPORT_SYMBOL(request_key_rcu);