On Tue, Mar 13, 2018 at 12:01 AM, Neil Horman <nhorman@xxxxxxxxxxxxx> wrote: > syzbot/kasan detected a double free in sctp_sendmsg_to_asoc: > BUG: KASAN: use-after-free in sctp_association_free+0x7b7/0x930 > net/sctp/associola.c:332 > Read of size 8 at addr ffff8801d8006ae0 by task syzkaller914861/4202 > > CPU: 1 PID: 4202 Comm: syzkaller914861 Not tainted 4.16.0-rc4+ #258 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google > 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:17 [inline] > dump_stack+0x194/0x24d lib/dump_stack.c:53 > print_address_description+0x73/0x250 mm/kasan/report.c:256 > kasan_report_error mm/kasan/report.c:354 [inline] > kasan_report+0x23c/0x360 mm/kasan/report.c:412 > __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 > sctp_association_free+0x7b7/0x930 net/sctp/associola.c:332 > sctp_sendmsg+0xc67/0x1a80 net/sctp/socket.c:2075 > inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763 > sock_sendmsg_nosec net/socket.c:629 [inline] > sock_sendmsg+0xca/0x110 net/socket.c:639 > SYSC_sendto+0x361/0x5c0 net/socket.c:1748 > SyS_sendto+0x40/0x50 net/socket.c:1716 > do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x42/0xb7 > > This was introduced by commit: > f84af33 sctp: factor out sctp_sendmsg_to_asoc from sctp_sendmsg > > As the newly refactored function moved the wait_for_sndbuf call to a > point after the association was connected, allowing for peeloff events > to occur, which in turn caused wait_for_sndbuf to return -EPIPE which > was not caught by the logic that determines if an association should be > freed or not. > > Fix it the easy way by returning the ordering of > sctp_primitive_ASSOCIATE and sctp_wait_for_sndbuf to the old order, to > ensure that EPIPE will not happen. > > Tested by myself using the syzbot reproducers with positive results > > Signed-off-by: Neil Horman <nhorman@xxxxxxxxxxxxx> > CC: davem@xxxxxxxxxxxxx > CC: Xin Long <lucien.xin@xxxxxxxxx> > Reported-by: syzbot+a4e4112c3aff00c8cfd8@xxxxxxxxxxxxxxxxxxxxxxxxx > --- > net/sctp/socket.c | 14 +++++++------- > 1 file changed, 7 insertions(+), 7 deletions(-) > > diff --git a/net/sctp/socket.c b/net/sctp/socket.c > index 7d3476a4860d..88c827b2becf 100644 > --- a/net/sctp/socket.c > +++ b/net/sctp/socket.c > @@ -1876,6 +1876,13 @@ static int sctp_sendmsg_to_asoc(struct sctp_association *asoc, > goto err; > } > > + if (!sctp_wspace(asoc)) { > + timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT); > + err = sctp_wait_for_sndbuf(asoc, &timeo, msg_len); > + if (err) > + goto err; > + } > + > if (sctp_state(asoc, CLOSED)) { > err = sctp_primitive_ASSOCIATE(net, asoc, NULL); > if (err) > @@ -1899,13 +1906,6 @@ static int sctp_sendmsg_to_asoc(struct sctp_association *asoc, > if (sctp_wspace(asoc) < msg_len) > sctp_prsctp_prune(asoc, sinfo, msg_len - sctp_wspace(asoc)); > Hi, Neil Do you mind moving these: if (asoc->pmtu_pending) sctp_assoc_pending_pmtu(asoc); if (sctp_wspace(asoc) < msg_len) sctp_prsctp_prune(asoc, sinfo, msg_len - sctp_wspace(asoc)); together with sctp_wait_for_sndbuf part up? especially, sctp_prsctp_prune has to be earlier than wait_for_sndbuf. And with prefix "sctp: " in subject and "Fixes:" tag in changelog would be nicer. > - if (!sctp_wspace(asoc)) { > - timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT); > - err = sctp_wait_for_sndbuf(asoc, &timeo, msg_len); > - if (err) > - goto err; > - } > - > datamsg = sctp_datamsg_from_user(asoc, sinfo, &msg->msg_iter); > if (IS_ERR(datamsg)) { > err = PTR_ERR(datamsg); > -- > 2.14.3 > -- 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