On Sat, Jul 23, 2016 at 04:00:39PM +0200, Vegard Nossum wrote: > On 07/23/2016 03:39 PM, Marcelo Ricardo Leitner wrote: > > On Sat, Jul 23, 2016 at 11:52:23AM +0200, Vegard Nossum wrote: > > > seq_read() can call ->start() twice on the same iterator more than once > > > (e.g. once through traverse() and once in seq_read() itself). > > > > But when traverse() returns the error, it goes to Done label, skipping > > the call to ->start() from seq_read(), or am I missing something? > > I think you're right. > > > Though yes, if sctp_ht_iter memory is actually re-used without > > initializting between seq_read()s, it triggers the issue you described. > > The sctp_ht_iter is allocated in > sctp_assocs_seq_open()/sctp_remaddr_seq_open(), so I assume it's > allocated on open(). > > > How did you trigger this, reading after an error on the file descriptor? > > I was using trinity, so I'm not quite sure a priori, but the problem was > 100% reproducible before I applied the patch and seeing that it gets > allocated on open() and is never cleared anywhere else, your suggestion > sounds like the most plausible explanation :-) > > How about rewording the first paragraph as: > > """ > sctp_transport_seq_start() does not currently clear iter->start_fail on > success, but relies on it being zero when it is allocated (by > seq_open_net()). > > This can be a problem in the following sequence: > > open() -- allocates iter (and implicitly sets iter->start_fail = 0) > read() > iter->start() -- fails and sets iter->start_fail = 1 > iter->stop() -- doesn't call sctp_transport_walk_stop() (correct) > read() again > iter->start() -- succeeds, but doesn't change iter->start_fail > iter->stop() -- doesn't call sctp_transport_walk_stop() (wrong) > """ > > Let me know how that sounds. LGTM, thanks! Marcelo > > Thanks for looking so closely at it! > > > Vegard > -- > To unsubscribe from this list: send the line "unsubscribe linux-sctp" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
