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Commit09f680d

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Fix race condition with BIO methods initialization in libpq with threads
The libpq code in charge of creating per-connection SSL objects wasprone to a race condition when loading the custom BIO methods needed bymy_SSL_set_fd(). As BIO methods are stored as a static variable, theinitialization of a connection could fail because it could be possibleto have one thread refer to my_bio_methods while it is being manipulatedby a second concurrent thread.This error has been introduced by8bb14cd, that has removedssl_config_mutex around the call of my_SSL_set_fd(), that itself setsthe custom BIO methods used in libpq. Like previously, the BIO methodinitialization is now protected by the existing ssl_config_mutex, itselfinitialized earlier for WIN32.While on it, document that my_bio_methods is protected byssl_config_mutex, as this can be easy to miss.Reported-by: Willi MannAuthor: Willi Mann, Michael PaquierDiscussion:https://postgr.es/m/e77abc4c-4d03-4058-a9d7-ef0035657e04@celonis.comBackpatch-through: 12
1 parent69a9134 commit09f680d

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+51
-22
lines changed

1 file changed

+51
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‎src/interfaces/libpq/fe-secure-openssl.c

Lines changed: 51 additions & 22 deletions
Original file line numberDiff line numberDiff line change
@@ -1607,6 +1607,7 @@ PQsslAttribute(PGconn *conn, const char *attribute_name)
16071607
#defineBIO_set_data(bio,data) (bio->ptr = data)
16081608
#endif
16091609

1610+
/* protected by ssl_config_mutex */
16101611
staticBIO_METHOD*my_bio_methods;
16111612

16121613
staticint
@@ -1672,6 +1673,15 @@ my_sock_write(BIO *h, const char *buf, int size)
16721673
staticBIO_METHOD*
16731674
my_BIO_s_socket(void)
16741675
{
1676+
BIO_METHOD*res;
1677+
1678+
#ifdefENABLE_THREAD_SAFETY
1679+
if (pthread_mutex_lock(&ssl_config_mutex))
1680+
returnNULL;
1681+
#endif
1682+
1683+
res=my_bio_methods;
1684+
16751685
if (!my_bio_methods)
16761686
{
16771687
BIO_METHOD*biom= (BIO_METHOD*)BIO_s_socket();
@@ -1680,39 +1690,58 @@ my_BIO_s_socket(void)
16801690

16811691
my_bio_index=BIO_get_new_index();
16821692
if (my_bio_index==-1)
1683-
returnNULL;
1693+
gotoerr;
16841694
my_bio_index |= (BIO_TYPE_DESCRIPTOR |BIO_TYPE_SOURCE_SINK);
1685-
my_bio_methods=BIO_meth_new(my_bio_index,"libpq socket");
1686-
if (!my_bio_methods)
1687-
returnNULL;
1695+
res=BIO_meth_new(my_bio_index,"libpq socket");
1696+
if (!res)
1697+
gotoerr;
16881698

16891699
/*
16901700
* As of this writing, these functions never fail. But check anyway,
16911701
* like OpenSSL's own examples do.
16921702
*/
1693-
if (!BIO_meth_set_write(my_bio_methods,my_sock_write)||
1694-
!BIO_meth_set_read(my_bio_methods,my_sock_read)||
1695-
!BIO_meth_set_gets(my_bio_methods,BIO_meth_get_gets(biom))||
1696-
!BIO_meth_set_puts(my_bio_methods,BIO_meth_get_puts(biom))||
1697-
!BIO_meth_set_ctrl(my_bio_methods,BIO_meth_get_ctrl(biom))||
1698-
!BIO_meth_set_create(my_bio_methods,BIO_meth_get_create(biom))||
1699-
!BIO_meth_set_destroy(my_bio_methods,BIO_meth_get_destroy(biom))||
1700-
!BIO_meth_set_callback_ctrl(my_bio_methods,BIO_meth_get_callback_ctrl(biom)))
1703+
if (!BIO_meth_set_write(res,my_sock_write)||
1704+
!BIO_meth_set_read(res,my_sock_read)||
1705+
!BIO_meth_set_gets(res,BIO_meth_get_gets(biom))||
1706+
!BIO_meth_set_puts(res,BIO_meth_get_puts(biom))||
1707+
!BIO_meth_set_ctrl(res,BIO_meth_get_ctrl(biom))||
1708+
!BIO_meth_set_create(res,BIO_meth_get_create(biom))||
1709+
!BIO_meth_set_destroy(res,BIO_meth_get_destroy(biom))||
1710+
!BIO_meth_set_callback_ctrl(res,BIO_meth_get_callback_ctrl(biom)))
17011711
{
1702-
BIO_meth_free(my_bio_methods);
1703-
my_bio_methods=NULL;
1704-
returnNULL;
1712+
gotoerr;
17051713
}
17061714
#else
1707-
my_bio_methods=malloc(sizeof(BIO_METHOD));
1708-
if (!my_bio_methods)
1709-
returnNULL;
1710-
memcpy(my_bio_methods,biom,sizeof(BIO_METHOD));
1711-
my_bio_methods->bread=my_sock_read;
1712-
my_bio_methods->bwrite=my_sock_write;
1715+
res=malloc(sizeof(BIO_METHOD));
1716+
if (!res)
1717+
gotoerr;
1718+
memcpy(res,biom,sizeof(BIO_METHOD));
1719+
res->bread=my_sock_read;
1720+
res->bwrite=my_sock_write;
17131721
#endif
17141722
}
1715-
returnmy_bio_methods;
1723+
1724+
my_bio_methods=res;
1725+
1726+
#ifdefENABLE_THREAD_SAFETY
1727+
pthread_mutex_unlock(&ssl_config_mutex);
1728+
#endif
1729+
1730+
returnres;
1731+
1732+
err:
1733+
#ifdefHAVE_BIO_METH_NEW
1734+
if (res)
1735+
BIO_meth_free(res);
1736+
#else
1737+
if (res)
1738+
free(res);
1739+
#endif
1740+
1741+
#ifdefENABLE_THREAD_SAFETY
1742+
pthread_mutex_unlock(&ssl_config_mutex);
1743+
#endif
1744+
returnNULL;
17161745
}
17171746

17181747
/* This should exactly match OpenSSL's SSL_set_fd except for using my BIO */

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