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Subject[PATCH 4.19 74/99] tipc: fix uninit-value in in tipc_conn_rcv_sub
Date
4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ying Xue <ying.xue@windriver.com>

commit a88289f4ddee4165d5f796bd99e09eec3133c16b upstream.

syzbot reported:

BUG: KMSAN: uninit-value in tipc_conn_rcv_sub+0x184/0x950 net/tipc/topsrv.c:373
CPU: 0 PID: 66 Comm: kworker/u4:4 Not tainted 4.17.0-rc3+ #88
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: tipc_rcv tipc_conn_recv_work
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x185/0x1d0 lib/dump_stack.c:113
kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
__msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:683
tipc_conn_rcv_sub+0x184/0x950 net/tipc/topsrv.c:373
tipc_conn_rcv_from_sock net/tipc/topsrv.c:409 [inline]
tipc_conn_recv_work+0x3cd/0x560 net/tipc/topsrv.c:424
process_one_work+0x12c6/0x1f60 kernel/workqueue.c:2145
worker_thread+0x113c/0x24f0 kernel/workqueue.c:2279
kthread+0x539/0x720 kernel/kthread.c:239
ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:412

Local variable description: ----s.i@tipc_conn_recv_work
Variable was created at:
tipc_conn_recv_work+0x65/0x560 net/tipc/topsrv.c:419
process_one_work+0x12c6/0x1f60 kernel/workqueue.c:2145

In tipc_conn_rcv_from_sock(), it always supposes the length of message
received from sock_recvmsg() is not smaller than the size of struct
tipc_subscr. However, this assumption is false. Especially when the
length of received message is shorter than struct tipc_subscr size,
we will end up touching uninitialized fields in tipc_conn_rcv_sub().

Reported-by: syzbot+8951a3065ee7fd6d6e23@syzkaller.appspotmail.com
Reported-by: syzbot+75e6e042c5bbf691fc82@syzkaller.appspotmail.com
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/tipc/topsrv.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/tipc/topsrv.c
+++ b/net/tipc/topsrv.c
@@ -404,7 +404,7 @@ static int tipc_conn_rcv_from_sock(struc
ret = sock_recvmsg(con->sock, &msg, MSG_DONTWAIT);
if (ret == -EWOULDBLOCK)
return -EWOULDBLOCK;
- if (ret > 0) {
+ if (ret == sizeof(s)) {
read_lock_bh(&sk->sk_callback_lock);
ret = tipc_conn_rcv_sub(srv, con, &s);
read_unlock_bh(&sk->sk_callback_lock);

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