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
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
---
Change notes
v2)
* Moved additional calls to restore origional ordering
* add sctp prefix
---
net/sctp/socket.c | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 7d3476a4860d..4bbfcf9532c2 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1876,6 +1876,19 @@ static int sctp_sendmsg_to_asoc(struct sctp_association *asoc,
goto err;
}
+ 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));
+
+ 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)
@@ -1893,19 +1906,6 @@ static int sctp_sendmsg_to_asoc(struct sctp_association *asoc,
pr_debug("%s: we associated primitively\n", __func__);
}
- 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));
-
- 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
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