Re: [Linux-kernel-mentees] [PATCH net] ipvs: Fix uninit-value in do_ip_vs_set_ctl()
From: Julian Anastasov <ja@ssi.bg>
Date: 2020-08-11 07:06:30
Also in:
lkml, lvs-devel, netdev, netfilter-devel
Hello, On Tue, 11 Aug 2020, Peilin Ye wrote:
On Mon, Aug 10, 2020 at 08:57:19PM -0700, Cong Wang wrote:quoted
On Mon, Aug 10, 2020 at 3:10 PM Peilin Ye [off-list ref] wrote:quoted
do_ip_vs_set_ctl() is referencing uninitialized stack value when `len` is zero. Fix it.Which exact 'cmd' is it here? I _guess_ it is one of those uninitialized in set_arglen[], which is 0.Yes, it was `IP_VS_SO_SET_NONE`, implicitly initialized to zero.quoted
But if that is the case, should it be initialized to sizeof(struct ip_vs_service_user) instead because ip_vs_copy_usvc_compat() is called anyway. Or, maybe we should just ban len==0 case.I see. I think the latter would be easier, but we cannot ban all of them, since the function does something with `IP_VS_SO_SET_FLUSH`, which is a `len == 0` case. Maybe we do something like this?
Yes, only IP_VS_SO_SET_FLUSH uses len 0. We can go with
this change but you do not need to target net tree, as the
problem is not fatal net-next works too. What happens is
that we may lookup services with random search keys which
is harmless.
Another option is to add new block after this one:
} else if (cmd == IP_VS_SO_SET_TIMEOUT) {
/* Set timeout values for (tcp tcpfin udp) */
ret = ip_vs_set_timeout(ipvs, (struct ip_vs_timeout_user *)arg);
goto out_unlock;
}
such as:
} else if (!len) {
/* No more commands with len=0 below */
ret = -EINVAL;
goto out_unlock;
}
It give more chance for future commands to use len=0
but the drawback is that the check happens under mutex. So, I'm
fine with both versions, it is up to you to decide :)
quoted hunk ↗ jump to hunk
@@ -2432,6 +2432,8 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len) if (cmd < IP_VS_BASE_CTL || cmd > IP_VS_SO_SET_MAX) return -EINVAL; + if (len == 0 && cmd != IP_VS_SO_SET_FLUSH) + return -EINVAL; if (len != set_arglen[CMDID(cmd)]) { IP_VS_DBG(1, "set_ctl: len %u != %u\n", len, set_arglen[CMDID(cmd)]);@@ -2547,9 +2549,6 @@ 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:
Regards -- Julian Anastasov [off-list ref] _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees