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Commit8984480

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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 parent9033e70 commit8984480

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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
@@ -1835,6 +1835,7 @@ PQsslAttribute(PGconn *conn, const char *attribute_name)
18351835
#defineBIO_set_data(bio,data) (bio->ptr = data)
18361836
#endif
18371837

1838+
/* protected by ssl_config_mutex */
18381839
staticBIO_METHOD*my_bio_methods;
18391840

18401841
staticint
@@ -1900,6 +1901,15 @@ my_sock_write(BIO *h, const char *buf, int size)
19001901
staticBIO_METHOD*
19011902
my_BIO_s_socket(void)
19021903
{
1904+
BIO_METHOD*res;
1905+
1906+
#ifdefENABLE_THREAD_SAFETY
1907+
if (pthread_mutex_lock(&ssl_config_mutex))
1908+
returnNULL;
1909+
#endif
1910+
1911+
res=my_bio_methods;
1912+
19031913
if (!my_bio_methods)
19041914
{
19051915
BIO_METHOD*biom= (BIO_METHOD*)BIO_s_socket();
@@ -1908,39 +1918,58 @@ my_BIO_s_socket(void)
19081918

19091919
my_bio_index=BIO_get_new_index();
19101920
if (my_bio_index==-1)
1911-
returnNULL;
1921+
gotoerr;
19121922
my_bio_index |= (BIO_TYPE_DESCRIPTOR |BIO_TYPE_SOURCE_SINK);
1913-
my_bio_methods=BIO_meth_new(my_bio_index,"libpq socket");
1914-
if (!my_bio_methods)
1915-
returnNULL;
1923+
res=BIO_meth_new(my_bio_index,"libpq socket");
1924+
if (!res)
1925+
gotoerr;
19161926

19171927
/*
19181928
* As of this writing, these functions never fail. But check anyway,
19191929
* like OpenSSL's own examples do.
19201930
*/
1921-
if (!BIO_meth_set_write(my_bio_methods,my_sock_write)||
1922-
!BIO_meth_set_read(my_bio_methods,my_sock_read)||
1923-
!BIO_meth_set_gets(my_bio_methods,BIO_meth_get_gets(biom))||
1924-
!BIO_meth_set_puts(my_bio_methods,BIO_meth_get_puts(biom))||
1925-
!BIO_meth_set_ctrl(my_bio_methods,BIO_meth_get_ctrl(biom))||
1926-
!BIO_meth_set_create(my_bio_methods,BIO_meth_get_create(biom))||
1927-
!BIO_meth_set_destroy(my_bio_methods,BIO_meth_get_destroy(biom))||
1928-
!BIO_meth_set_callback_ctrl(my_bio_methods,BIO_meth_get_callback_ctrl(biom)))
1931+
if (!BIO_meth_set_write(res,my_sock_write)||
1932+
!BIO_meth_set_read(res,my_sock_read)||
1933+
!BIO_meth_set_gets(res,BIO_meth_get_gets(biom))||
1934+
!BIO_meth_set_puts(res,BIO_meth_get_puts(biom))||
1935+
!BIO_meth_set_ctrl(res,BIO_meth_get_ctrl(biom))||
1936+
!BIO_meth_set_create(res,BIO_meth_get_create(biom))||
1937+
!BIO_meth_set_destroy(res,BIO_meth_get_destroy(biom))||
1938+
!BIO_meth_set_callback_ctrl(res,BIO_meth_get_callback_ctrl(biom)))
19291939
{
1930-
BIO_meth_free(my_bio_methods);
1931-
my_bio_methods=NULL;
1932-
returnNULL;
1940+
gotoerr;
19331941
}
19341942
#else
1935-
my_bio_methods=malloc(sizeof(BIO_METHOD));
1936-
if (!my_bio_methods)
1937-
returnNULL;
1938-
memcpy(my_bio_methods,biom,sizeof(BIO_METHOD));
1939-
my_bio_methods->bread=my_sock_read;
1940-
my_bio_methods->bwrite=my_sock_write;
1943+
res=malloc(sizeof(BIO_METHOD));
1944+
if (!res)
1945+
gotoerr;
1946+
memcpy(res,biom,sizeof(BIO_METHOD));
1947+
res->bread=my_sock_read;
1948+
res->bwrite=my_sock_write;
19411949
#endif
19421950
}
1943-
returnmy_bio_methods;
1951+
1952+
my_bio_methods=res;
1953+
1954+
#ifdefENABLE_THREAD_SAFETY
1955+
pthread_mutex_unlock(&ssl_config_mutex);
1956+
#endif
1957+
1958+
returnres;
1959+
1960+
err:
1961+
#ifdefHAVE_BIO_METH_NEW
1962+
if (res)
1963+
BIO_meth_free(res);
1964+
#else
1965+
if (res)
1966+
free(res);
1967+
#endif
1968+
1969+
#ifdefENABLE_THREAD_SAFETY
1970+
pthread_mutex_unlock(&ssl_config_mutex);
1971+
#endif
1972+
returnNULL;
19441973
}
19451974

19461975
/* This should exactly match OpenSSL's SSL_set_fd except for using my BIO */

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