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Commitc3b7922

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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 parent648fc6a commitc3b7922

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1 file changed

+51
-22
lines changed

1 file changed

+51
-22
lines changed

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

Lines changed: 51 additions & 22 deletions
Original file line numberDiff line numberDiff line change
@@ -1666,6 +1666,7 @@ PQsslAttribute(PGconn *conn, const char *attribute_name)
16661666
#defineBIO_set_data(bio,data) (bio->ptr = data)
16671667
#endif
16681668

1669+
/* protected by ssl_config_mutex */
16691670
staticBIO_METHOD*my_bio_methods;
16701671

16711672
staticint
@@ -1731,6 +1732,15 @@ my_sock_write(BIO *h, const char *buf, int size)
17311732
staticBIO_METHOD*
17321733
my_BIO_s_socket(void)
17331734
{
1735+
BIO_METHOD*res;
1736+
1737+
#ifdefENABLE_THREAD_SAFETY
1738+
if (pthread_mutex_lock(&ssl_config_mutex))
1739+
returnNULL;
1740+
#endif
1741+
1742+
res=my_bio_methods;
1743+
17341744
if (!my_bio_methods)
17351745
{
17361746
BIO_METHOD*biom= (BIO_METHOD*)BIO_s_socket();
@@ -1739,39 +1749,58 @@ my_BIO_s_socket(void)
17391749

17401750
my_bio_index=BIO_get_new_index();
17411751
if (my_bio_index==-1)
1742-
returnNULL;
1752+
gotoerr;
17431753
my_bio_index |= (BIO_TYPE_DESCRIPTOR |BIO_TYPE_SOURCE_SINK);
1744-
my_bio_methods=BIO_meth_new(my_bio_index,"libpq socket");
1745-
if (!my_bio_methods)
1746-
returnNULL;
1754+
res=BIO_meth_new(my_bio_index,"libpq socket");
1755+
if (!res)
1756+
gotoerr;
17471757

17481758
/*
17491759
* As of this writing, these functions never fail. But check anyway,
17501760
* like OpenSSL's own examples do.
17511761
*/
1752-
if (!BIO_meth_set_write(my_bio_methods,my_sock_write)||
1753-
!BIO_meth_set_read(my_bio_methods,my_sock_read)||
1754-
!BIO_meth_set_gets(my_bio_methods,BIO_meth_get_gets(biom))||
1755-
!BIO_meth_set_puts(my_bio_methods,BIO_meth_get_puts(biom))||
1756-
!BIO_meth_set_ctrl(my_bio_methods,BIO_meth_get_ctrl(biom))||
1757-
!BIO_meth_set_create(my_bio_methods,BIO_meth_get_create(biom))||
1758-
!BIO_meth_set_destroy(my_bio_methods,BIO_meth_get_destroy(biom))||
1759-
!BIO_meth_set_callback_ctrl(my_bio_methods,BIO_meth_get_callback_ctrl(biom)))
1762+
if (!BIO_meth_set_write(res,my_sock_write)||
1763+
!BIO_meth_set_read(res,my_sock_read)||
1764+
!BIO_meth_set_gets(res,BIO_meth_get_gets(biom))||
1765+
!BIO_meth_set_puts(res,BIO_meth_get_puts(biom))||
1766+
!BIO_meth_set_ctrl(res,BIO_meth_get_ctrl(biom))||
1767+
!BIO_meth_set_create(res,BIO_meth_get_create(biom))||
1768+
!BIO_meth_set_destroy(res,BIO_meth_get_destroy(biom))||
1769+
!BIO_meth_set_callback_ctrl(res,BIO_meth_get_callback_ctrl(biom)))
17601770
{
1761-
BIO_meth_free(my_bio_methods);
1762-
my_bio_methods=NULL;
1763-
returnNULL;
1771+
gotoerr;
17641772
}
17651773
#else
1766-
my_bio_methods=malloc(sizeof(BIO_METHOD));
1767-
if (!my_bio_methods)
1768-
returnNULL;
1769-
memcpy(my_bio_methods,biom,sizeof(BIO_METHOD));
1770-
my_bio_methods->bread=my_sock_read;
1771-
my_bio_methods->bwrite=my_sock_write;
1774+
res=malloc(sizeof(BIO_METHOD));
1775+
if (!res)
1776+
gotoerr;
1777+
memcpy(res,biom,sizeof(BIO_METHOD));
1778+
res->bread=my_sock_read;
1779+
res->bwrite=my_sock_write;
17721780
#endif
17731781
}
1774-
returnmy_bio_methods;
1782+
1783+
my_bio_methods=res;
1784+
1785+
#ifdefENABLE_THREAD_SAFETY
1786+
pthread_mutex_unlock(&ssl_config_mutex);
1787+
#endif
1788+
1789+
returnres;
1790+
1791+
err:
1792+
#ifdefHAVE_BIO_METH_NEW
1793+
if (res)
1794+
BIO_meth_free(res);
1795+
#else
1796+
if (res)
1797+
free(res);
1798+
#endif
1799+
1800+
#ifdefENABLE_THREAD_SAFETY
1801+
pthread_mutex_unlock(&ssl_config_mutex);
1802+
#endif
1803+
returnNULL;
17751804
}
17761805

17771806
/* This should exactly match OpenSSL's SSL_set_fd except for using my BIO */

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