From 5278bbfe0c79c1f2b5bf8a215d8e7d63f1900ce9 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Thu, 16 Jun 2016 18:37:11 +0200 Subject: [PATCH] resolved: when restarting a transaction make sure to not touch it anymore (#3553) dns_transaction_maybe_restart() is supposed to return 1 if the the transaction has been restarted and 0 otherwise. dns_transaction_process_dnssec() relies on this behaviour. Before this change in case of restart we'd call dns_transaction_go() when restarting the lookup, returning its return value unmodified. This is wrong however, as that function returns 1 if the transaction is pending, and 0 if it completed immediately, which is a very different set of return values. Fix this, by always returning 1 on redirection. The wrong return value resulted in all kinds of bad memory accesses as we might continue processing a transaction that was redirected and completed immediately (and thus freed). This patch also adds comments to the two functions to clarify the return values for the future. Most likely fixes: #2942 #3475 #3484 --- src/resolve/resolved-dns-transaction.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c index ed18df35cb..bcb1b6d8a7 100644 --- a/src/resolve/resolved-dns-transaction.c +++ b/src/resolve/resolved-dns-transaction.c @@ -404,8 +404,12 @@ static void dns_transaction_retry(DnsTransaction *t) { } static int dns_transaction_maybe_restart(DnsTransaction *t) { + int r; + assert(t); + /* Returns > 0 if the transaction was restarted, 0 if not */ + if (!t->server) return 0; @@ -420,7 +424,12 @@ static int dns_transaction_maybe_restart(DnsTransaction *t) { log_debug("Server feature level is now lower than when we began our transaction. Restarting with new ID."); dns_transaction_shuffle_id(t); - return dns_transaction_go(t); + + r = dns_transaction_go(t); + if (r < 0) + return r; + + return 1; } static int on_stream_complete(DnsStream *s, int error) { @@ -1421,6 +1430,9 @@ int dns_transaction_go(DnsTransaction *t) { assert(t); + /* Returns > 0 if the transaction is now pending, returns 0 if could be processed immediately and has finished + * now. */ + assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); r = dns_transaction_prepare(t, ts);