From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Ricardo Leitner Subject: Re: [PATCH RESEND] net/sctp: always initialise sctp_ht_iter::start_fail Date: Fri, 12 Aug 2016 11:41:42 -0300 Message-ID: <20160812144142.GB3110@localhost.localdomain> References: <1470988251-18792-1-git-send-email-vegard.nossum@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-sctp@vger.kernel.org, Xin Long , Herbert Xu , "Eric W. Biederman" , stable@vger.kernel.org To: Vegard Nossum Return-path: Received: from mx1.redhat.com ([209.132.183.28]:42022 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752305AbcHLOmG (ORCPT ); Fri, 12 Aug 2016 10:42:06 -0400 Content-Disposition: inline In-Reply-To: <1470988251-18792-1-git-send-email-vegard.nossum@oracle.com> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Aug 12, 2016 at 09:50:51AM +0200, Vegard Nossum wrote: > 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) > > We should initialize sctp_ht_iter::start_fail to zero if ->start() > succeeds, otherwise it's possible that we leave an old value of 1 there, > which will cause ->stop() to not call sctp_transport_walk_stop(), which > causes all sorts of problems like not calling rcu_read_unlock() (and > preempt_enable()), eventually leading to more warnings like this: > > BUG: sleeping function called from invalid context at mm/slab.h:388 > in_atomic(): 0, irqs_disabled(): 0, pid: 16551, name: trinity-c2 > Preemption disabled at:[] rhashtable_walk_start+0x46/0x150 > > [] preempt_count_add+0x1fb/0x280 > [] _raw_spin_lock+0x12/0x40 > [] rhashtable_walk_start+0x46/0x150 > [] sctp_transport_walk_start+0x2f/0x60 > [] sctp_transport_seq_start+0x4d/0x150 > [] traverse+0x170/0x850 > [] seq_read+0x7cc/0x1180 > [] proc_reg_read+0xbc/0x180 > [] do_loop_readv_writev+0x134/0x210 > [] do_readv_writev+0x565/0x660 > [] vfs_readv+0x67/0xa0 > [] do_preadv+0x126/0x170 > [] SyS_preadv+0xc/0x10 > [] do_syscall_64+0x19c/0x410 > [] return_from_SYSCALL_64+0x0/0x6a > [] 0xffffffffffffffff > > Notice that this is a subtly different stacktrace from the one in commit > 5fc382d875 ("net/sctp: terminate rhashtable walk correctly"). > > Cc: Xin Long > Cc: Herbert Xu > Cc: Eric W. Biederman > Cc: Marcelo Ricardo Leitner > Cc: stable@vger.kernel.org > Signed-off-by: Vegard Nossum Acked-by: Marcelo Ricardo Leitner Thanks > --- > net/sctp/proc.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/net/sctp/proc.c b/net/sctp/proc.c > index 4cb5aed..ef8ba77 100644 > --- a/net/sctp/proc.c > +++ b/net/sctp/proc.c > @@ -293,6 +293,7 @@ static void *sctp_transport_seq_start(struct seq_file *seq, loff_t *pos) > return ERR_PTR(err); > } > > + iter->start_fail = 0; > return sctp_transport_get_idx(seq_file_net(seq), &iter->hti, *pos); > } > > -- > 1.9.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-sctp" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >