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Don't take a write lock when freeing an EVP_PKEY

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When freeing the last reference to an EVP_PKEY there is no point in
taking the lock for the key. It is the last reference and is being freed
so must only be being used by a single thread.

This should not have been the source of any contention so its unclear to
what extent this will improve performance. But we should not be locking
when we don't need to.

Partially fixes #20286

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20932)
This commit is contained in:
Matt Caswell 2023-05-10 16:27:03 +01:00 committed by Tomas Mraz
parent 95a8aa6dc0
commit 36424806d6
4 changed files with 8 additions and 13 deletions
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8
crypto/evp/keymgmt_lib.c
View File

@ -194,7 +194,7 @@ void *evp_keymgmt_util_export_to_provider(EVP_PKEY *pk, EVP_KEYMGMT *keymgmt,
* operation cache. In that case, we know that |i| is zero.
*/
if (pk->dirty_cnt != pk->dirty_cnt_copy)
evp_keymgmt_util_clear_operation_cache(pk, 0);
evp_keymgmt_util_clear_operation_cache(pk);
/* Add the new export to the operation cache */
if (!evp_keymgmt_util_cache_keydata(pk, keymgmt, import_data.keydata,
@ -219,15 +219,11 @@ static void op_cache_free(OP_CACHE_ELEM *e)
OPENSSL_free(e);
}
int evp_keymgmt_util_clear_operation_cache(EVP_PKEY *pk, int locking)
int evp_keymgmt_util_clear_operation_cache(EVP_PKEY *pk)
{
if (pk != NULL) {
if (locking && pk->lock != NULL && !CRYPTO_THREAD_write_lock(pk->lock))
return 0;
sk_OP_CACHE_ELEM_pop_free(pk->operation_cache, op_cache_free);
pk->operation_cache = NULL;
if (locking && pk->lock != NULL)
CRYPTO_THREAD_unlock(pk->lock);
}
return 1;

4
crypto/evp/p_lib.c
View File

@ -1757,7 +1757,7 @@ void evp_pkey_free_legacy(EVP_PKEY *x)
static void evp_pkey_free_it(EVP_PKEY *x)
{
/* internal function; x is never NULL */
evp_keymgmt_util_clear_operation_cache(x, 1);
evp_keymgmt_util_clear_operation_cache(x);
#ifndef FIPS_MODULE
evp_pkey_free_legacy(x);
#endif
@ -1936,7 +1936,7 @@ void *evp_pkey_export_to_provider(EVP_PKEY *pk, OSSL_LIB_CTX *libctx,
if (!CRYPTO_THREAD_write_lock(pk->lock))
goto end;
if (pk->ameth->dirty_cnt(pk) != pk->dirty_cnt_copy
&& !evp_keymgmt_util_clear_operation_cache(pk, 0)) {
&& !evp_keymgmt_util_clear_operation_cache(pk)) {
CRYPTO_THREAD_unlock(pk->lock);
evp_keymgmt_freedata(tmp_keymgmt, keydata);
keydata = NULL;

7
doc/internal/man3/evp_keymgmt_util_export_to_provider.pod
View File

@ -25,7 +25,7 @@ OP_CACHE_ELEM
OP_CACHE_ELEM *evp_keymgmt_util_find_operation_cache(EVP_PKEY *pk,
EVP_KEYMGMT *keymgmt,
int selection);
int evp_keymgmt_util_clear_operation_cache(EVP_PKEY *pk, int locking);
int evp_keymgmt_util_clear_operation_cache(EVP_PKEY *pk);
int evp_keymgmt_util_cache_keydata(EVP_PKEY *pk, EVP_KEYMGMT *keymgmt,
void *keydata, int selection);
void evp_keymgmt_util_cache_keyinfo(EVP_PKEY *pk);
@ -52,9 +52,8 @@ I<keymgmt> in I<pk>'s cache of provided keys for operations.
It should only be called while holding I<pk>'s lock (read or write).
evp_keymgmt_util_clear_operation_cache() can be used to explicitly
clear the cache of operation key references. If I<locking> is set to 1 then
then I<pk>'s lock will be obtained while doing the clear. Otherwise it will be
assumed that the lock has already been obtained or is not required.
clear the cache of operation key references. If required the lock must already
have been obtained.
evp_keymgmt_util_cache_keydata() can be used to add a provider key
object to a B<PKEY>.

2
include/crypto/evp.h
View File

@ -785,7 +785,7 @@ void *evp_keymgmt_util_export_to_provider(EVP_PKEY *pk, EVP_KEYMGMT *keymgmt,
OP_CACHE_ELEM *evp_keymgmt_util_find_operation_cache(EVP_PKEY *pk,
EVP_KEYMGMT *keymgmt,
int selection);
int evp_keymgmt_util_clear_operation_cache(EVP_PKEY *pk, int locking);
int evp_keymgmt_util_clear_operation_cache(EVP_PKEY *pk);
int evp_keymgmt_util_cache_keydata(EVP_PKEY *pk, EVP_KEYMGMT *keymgmt,
void *keydata, int selection);
void evp_keymgmt_util_cache_keyinfo(EVP_PKEY *pk);