commit 91d7cf50c6cb6eb1e2dc2b4a8eab489c10a759a6 Author: Nick Mathewson nickm@torproject.org Date: Fri Mar 11 10:50:36 2016 -0500

Change behavior on missing/present event to warn instead of asserting.

Add a changes file. --- changes/bug16248 | 8 ++++++++ src/or/main.c | 49 +++++++++++++++++++++++++++++++++++++------------ 2 files changed, 45 insertions(+), 12 deletions(-)

diff --git a/changes/bug16248 b/changes/bug16248 new file mode 100644 index 0000000..399b709 --- /dev/null +++ b/changes/bug16248 @@ -0,0 +1,8 @@ + o Major bugfixes (dns proxy mode, crash): + - Avoid crashing when running as a DNS proxy. Closes bug 16248; bugfix on + 0.2.0.1-alpha. Patch from 'cypherpunks'. + + o Minor features (bug-resistance): + - Make Tor survive errors involving connections without a corresponding + event object. Previously we'd fail with an assertion; now we produce a + log message. Related to bug 16248. diff --git a/src/or/main.c b/src/or/main.c index 3fb80e1..f91049b 100644 --- a/src/or/main.c +++ b/src/or/main.c @@ -567,6 +567,35 @@ connection_is_reading(connection_t *conn) (conn->read_event && event_pending(conn->read_event, EV_READ, NULL)); }

+static int +connection_check_event(connection_t *conn, struct event *ev) +{ + int bad; + + if (conn->type == CONN_TYPE_AP && TO_EDGE_CONN(conn)->is_dns_request) { + bad = ev != NULL; + } else { + bad = ev == NULL; + } + + if (bad) { + log_warn(LD_BUG, "Event missing on connection %p [%s;%s]. " + "socket=%d. linked=%d. " + "is_dns_request=%d. Marked_for_close=%s:%d", + conn, + conn_type_to_string(conn->type), + conn_state_to_string(conn->type, conn->state), + (int)conn->s, (int)conn->linked, + (conn->type == CONN_TYPE_AP && TO_EDGE_CONN(conn)->is_dns_request), + conn->marked_for_close_file ? conn->marked_for_close_file : "-", + conn->marked_for_close + ); + log_backtrace(LOG_WARN, LD_BUG, "Backtrace attached."); + return -1; + } + return 0; +} + /** Tell the main loop to stop notifying <b>conn</b> of any read events. */ MOCK_IMPL(void, connection_stop_reading,(connection_t *conn)) @@ -578,14 +607,10 @@ connection_stop_reading,(connection_t *conn)) return; });

- /* if dummy conn then no socket and no event, nothing to do here */ - if (conn->type == CONN_TYPE_AP && TO_EDGE_CONN(conn)->is_dns_request) { - tor_assert(!conn->read_event); + if (connection_check_event(conn, conn->read_event) < 0) { return; }

- tor_assert(conn->read_event); - if (conn->linked) { conn->reading_from_linked_conn = 0; connection_stop_reading_from_linked_conn(conn); @@ -609,14 +634,10 @@ connection_start_reading,(connection_t *conn)) return; });

- /* if dummy conn then no socket and no event, nothing to do here */ - if (conn->type == CONN_TYPE_AP && TO_EDGE_CONN(conn)->is_dns_request) { - tor_assert(!conn->read_event); + if (connection_check_event(conn, conn->read_event) < 0) { return; }

- tor_assert(conn->read_event); - if (conn->linked) { conn->reading_from_linked_conn = 1; if (connection_should_read_from_linked_conn(conn)) @@ -655,7 +676,9 @@ connection_stop_writing,(connection_t *conn)) return; });

- tor_assert(conn->write_event); + if (connection_check_event(conn, conn->write_event) < 0) { + return; + }

if (conn->linked) { conn->writing_to_linked_conn = 0; @@ -681,7 +704,9 @@ connection_start_writing,(connection_t *conn)) return; });

- tor_assert(conn->write_event); + if (connection_check_event(conn, conn->write_event) < 0) { + return; + }

if (conn->linked) { conn->writing_to_linked_conn = 1;