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

To: Wensong Zhang <wensong@xxxxxxxxxxxx>, Simon Horman <horms@xxxxxxxxxxxx>, Julian Anastasov <ja@xxxxxx>
Subject: [Linux-kernel-mentees] [PATCH net-next v2] ipvs: Fix uninit-value in do_ip_vs_set_ctl()
Cc: Peilin Ye <yepeilin.cs@xxxxxxxxx>, Cong Wang <xiyou.wangcong@xxxxxxxxx>, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>, Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxx>, Florian Westphal <fw@xxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, Jakub Kicinski <kuba@xxxxxxxxxx>, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>, netdev@xxxxxxxxxxxxxxx, lvs-devel@xxxxxxxxxxxxxxx, netfilter-devel@xxxxxxxxxxxxxxx, coreteam@xxxxxxxxxxxxx, linux-kernel-mentees@xxxxxxxxxxxxxxxxxxxxxxxxx, syzkaller-bugs@xxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
From: Peilin Ye <yepeilin.cs@xxxxxxxxx>
Date: Tue, 11 Aug 2020 03:46:40 -0400
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


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