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Merge remote-tracking branch 'origin/maint-0.2.3'
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commit
c49975a2b8
5
changes/bug6480
Normal file
5
changes/bug6480
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@ -0,0 +1,5 @@
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o Major bugfixes:
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- Avoid read-from-freed-RAM bug and related double-free bug that
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could occur when a DNS request fails while launching it. Fixes
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bug 6480; bugfix on 0.2.0.1-alpha.
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30
src/or/dns.c
30
src/or/dns.c
@ -168,7 +168,8 @@ static void add_wildcarded_test_address(const char *address);
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static int configure_nameservers(int force);
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static int answer_is_wildcarded(const char *ip);
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static int dns_resolve_impl(edge_connection_t *exitconn, int is_resolve,
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or_circuit_t *oncirc, char **resolved_to_hostname);
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or_circuit_t *oncirc, char **resolved_to_hostname,
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int *made_connection_pending_out);
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#ifdef DEBUG_DNS_CACHE
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static void _assert_cache_ok(void);
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#define assert_cache_ok() _assert_cache_ok()
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@ -596,10 +597,12 @@ dns_resolve(edge_connection_t *exitconn)
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{
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or_circuit_t *oncirc = TO_OR_CIRCUIT(exitconn->on_circuit);
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int is_resolve, r;
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int made_connection_pending = 0;
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char *hostname = NULL;
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is_resolve = exitconn->_base.purpose == EXIT_PURPOSE_RESOLVE;
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r = dns_resolve_impl(exitconn, is_resolve, oncirc, &hostname);
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r = dns_resolve_impl(exitconn, is_resolve, oncirc, &hostname,
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&made_connection_pending);
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switch (r) {
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case 1:
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@ -639,16 +642,11 @@ dns_resolve(edge_connection_t *exitconn)
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dns_cancel_pending_resolve(exitconn->_base.address);
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if (!exitconn->_base.marked_for_close) {
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if (!made_connection_pending && !exitconn->_base.marked_for_close) {
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/* If we made the connection pending, then we freed it already in
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* dns_cancel_pending_resolve(). If we marked it for close, it'll
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* get freed from the main loop. Otherwise, can free it now. */
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connection_free(TO_CONN(exitconn));
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// XXX ... and we just leak exitconn otherwise? -RD
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// If it's marked for close, it's on closeable_connection_lst in
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// main.c. If it's on the closeable list, it will get freed from
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// main.c. -NM
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// "<armadev> If that's true, there are other bugs around, where we
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// don't check if it's marked, and will end up double-freeing."
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// On the other hand, I don't know of any actual bugs here, so this
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// shouldn't be holding up the rc. -RD
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}
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break;
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default:
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@ -667,10 +665,15 @@ dns_resolve(edge_connection_t *exitconn)
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* Return -2 on a transient error. If it's a reverse resolve and it's
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* successful, sets *<b>hostname_out</b> to a newly allocated string
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* holding the cached reverse DNS value.
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*
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* Set *<b>made_connection_pending_out</b> to true if we have placed
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* <b>exitconn</b> on the list of pending connections for some resolve; set it
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* to false otherwise.
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*/
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static int
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dns_resolve_impl(edge_connection_t *exitconn, int is_resolve,
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or_circuit_t *oncirc, char **hostname_out)
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or_circuit_t *oncirc, char **hostname_out,
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int *made_connection_pending_out)
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{
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cached_resolve_t *resolve;
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cached_resolve_t search;
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@ -684,6 +687,7 @@ dns_resolve_impl(edge_connection_t *exitconn, int is_resolve,
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tor_assert(!SOCKET_OK(exitconn->_base.s));
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assert_cache_ok();
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tor_assert(oncirc);
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*made_connection_pending_out = 0;
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/* first check if exitconn->_base.address is an IP. If so, we already
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* know the answer. */
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@ -757,6 +761,7 @@ dns_resolve_impl(edge_connection_t *exitconn, int is_resolve,
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pending_connection->conn = exitconn;
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pending_connection->next = resolve->pending_connections;
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resolve->pending_connections = pending_connection;
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*made_connection_pending_out = 1;
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log_debug(LD_EXIT,"Connection (fd %d) waiting for pending DNS "
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"resolve of %s", exitconn->_base.s,
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escaped_safe_str(exitconn->_base.address));
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@ -797,6 +802,7 @@ dns_resolve_impl(edge_connection_t *exitconn, int is_resolve,
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pending_connection = tor_malloc_zero(sizeof(pending_connection_t));
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pending_connection->conn = exitconn;
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resolve->pending_connections = pending_connection;
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*made_connection_pending_out = 1;
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/* Add this resolve to the cache and priority queue. */
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HT_INSERT(cache_map, &cache_root, resolve);
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