I reply to myself: while the version in Xenial is *still* affected with this bug, any of the later versions is fixed. The version 2.1.26.dfsg1-14 is bugged, but the next one, 2.1.26.dfsg1-15 is not. I backported the one in Bionic easily and it's working now without problems.
-- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to cyrus-sasl2 in Ubuntu. https://bugs.launchpad.net/bugs/997217 Title: salsauthd maxes cpu Status in cyrus-sasl2 package in Ubuntu: Fix Released Status in cyrus-sasl2 source package in Precise: Triaged Bug description: sasl2-bin version 2.1.24~rc1.dfsg1+cvs2011-05-23-4ubuntu contains a bug that causes heavy cpu utilization, impacting normal operation of one of our mail servers following an upgrade to Ubuntu 12.04. We are running the daemon with the following options: /usr/sbin/saslauthd -a rimap -O our.imap.server -r -m /var/spool/postfix/var/run/saslauthd -n 5 We noticed that users were unable to send mail and that the saslauthd processes were using approximately 100% of each cpu core. An strace of one of the runaway process showed that it was stuck in the following behaviour: select(9, [8], NULL, NULL, {0, 0}) = 1 (in [8], left {0, 0}) read(8, "", 940) = 0 select(9, [8], NULL, NULL, {0, 0}) = 1 (in [8], left {0, 0}) read(8, "", 940) = 0 select(9, [8], NULL, NULL, {0, 0}) = 1 (in [8], left {0, 0}) read(8, "", 940) = 0 select(9, [8], NULL, NULL, {0, 0}) = 1 (in [8], left {0, 0}) read(8, "", 940) = 0 select(9, [8], NULL, NULL, {0, 0}) = 1 (in [8], left {0, 0}) read(8, "", 940) = 0 select(9, [8], NULL, NULL, {0, 0}) = 1 (in [8], left {0, 0}) read(8, "", 940) = 0 select(9, [8], NULL, NULL, {0, 0}) = 1 (in [8], left {0, 0}) read(8, "", 940) = 0 ..... with further inspection showing that the file descriptor in question was a socket connected to our imap server in CLOSE_WAIT. Browsing saslauthd/auth_rimap.c in the source package for sasl2-bin, we came across the following code, repeated in two locations: while( select (fds, &perm, NULL, NULL, &timeout ) >0 ) { if ( FD_ISSET(s, &perm) ) { ret = read(s, rbuf+rc, sizeof(rbuf)-rc); if ( ret<0 ) { rc = ret; break; } else { rc += ret; } } } It looks like this loop is expected to run until a read error is encountered or the timeout of 1 second is reached. There is no test to check that 0 bytes were read, indicating that the connection was closed by the remote peer. Since select() will immediately return the size of the set of the partially closed descriptor (1, which is >0), and calls to read() will always yield 0 bytes, there's the potential for execution to get stuck in this non blocking loop and I'm presuming that that's what's happening here. We've not performed any further analysis to prove that this is really what's happening but if my intuition is correct then our IMAP server (an nginx imap proxy) most liklely closes the connection at an unexpected time under as yet undetermined conditions. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/cyrus-sasl2/+bug/997217/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
