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Prevent an (impossible) null-pointer dereference in connection_edge_process_relay_cell

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This would happen if the deliver window could become negative
because of an nonexistent connection.  (Fortunately, _that_ can't
occur, thanks to circuit_consider_sending_sendme.  Still, if we
change our windowing logic at all, we won't want this to become
triggerable.)  Fix for bug 5541.  Bugfix on 4a66865d, back from
0.0.2pre14.  asn found this.  Nice catch, asn!
This commit is contained in:
Nick Mathewson 2012-03-31 14:17:41 -04:00
parent 9740f067c4
commit edf0d5b12c
2 changed files with 14 additions and 2 deletions
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8
changes/bug5541 Normal file
View File

@ -0,0 +1,8 @@
o Minor bugfixes:
- Prevent a null-pointer dereference when receiving a data cell
for a nonexistent stream when the circuit in question has an
empty deliver window. We don't believe this is triggerable,
since we don't currently allow deliver windows to become empty,
but the logic is tricky enough that it's better to make the code
robust. Fixes bug 5541; bugfix on 0.0.2pre14.

8
src/or/relay.c
View File

@ -1103,8 +1103,12 @@ connection_edge_process_relay_cell(cell_t *cell, circuit_t *circ,
(!layer_hint && --circ->deliver_window < 0)) {
log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
"(relay data) circ deliver_window below 0. Killing.");
connection_edge_end(conn, END_STREAM_REASON_TORPROTOCOL);
connection_mark_for_close(TO_CONN(conn));
if (conn) {
/* XXXX Do we actually need to do this? Will killing the circuit
* not send an END and mark the stream for close as appropriate? */
connection_edge_end(conn, END_STREAM_REASON_TORPROTOCOL);
connection_mark_for_close(TO_CONN(conn));
}
return -END_CIRC_REASON_TORPROTOCOL;
}
log_debug(domain,"circ deliver_window now %d.", layer_hint ?