[Linux-kernel-mentees] [PATCH net-next v2] ipvs: Fix uninit-value in do_ip_vs_set_ctl()

From: Peilin Ye
Date: Tue Aug 11 2020 - 03:49:21 EST


do_ip_vs_set_ctl() is referencing uninitialized stack value when `len` is
zero. Fix it.

Reported-by: syzbot+23b5f9e7caf61d9a3898@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://syzkaller.appspot.com/bug?id=46ebfb92a8a812621a001ef04d90dfa459520fe2
Suggested-by: Julian Anastasov <ja@xxxxxx>
Signed-off-by: Peilin Ye <yepeilin.cs@xxxxxxxxx>
---
Changes in v2:
- Target net-next tree. (Suggested by Julian Anastasov <ja@xxxxxx>)
- Reject all `len == 0` requests except `IP_VS_SO_SET_FLUSH`, instead
of initializing `arg`. (Suggested by Cong Wang
<xiyou.wangcong@xxxxxxxxx>, Julian Anastasov <ja@xxxxxx>)

net/netfilter/ipvs/ip_vs_ctl.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 412656c34f20..beeafa42aad7 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -2471,6 +2471,10 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
/* Set timeout values for (tcp tcpfin udp) */
ret = ip_vs_set_timeout(ipvs, (struct ip_vs_timeout_user *)arg);
goto out_unlock;
+ } else if (!len) {
+ /* No more commands with len == 0 below */
+ ret = -EINVAL;
+ goto out_unlock;
}

usvc_compat = (struct ip_vs_service_user *)arg;
@@ -2547,9 +2551,6 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
break;
case IP_VS_SO_SET_DELDEST:
ret = ip_vs_del_dest(svc, &udest);
- break;
- default:
- ret = -EINVAL;
}

out_unlock:
--
2.25.1