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

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

[Peilin Ye]

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

Reported-and-tested-by: syzbot+23b5f9e7caf61d9a3898@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=46ebfb92a8a812621a001ef04d90dfa459520fe2
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
---
 net/netfilter/ipvs/ip_vs_ctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 412656c34f20..c050b6a42786 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -2418,7 +2418,7 @@ do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
 {
 	struct net *net = sock_net(sk);
 	int ret;
-	unsigned char arg[MAX_SET_ARGLEN];
+	unsigned char arg[MAX_SET_ARGLEN] = {};
 	struct ip_vs_service_user *usvc_compat;
 	struct ip_vs_service_user_kern usvc;
 	struct ip_vs_service *svc;
-- 
2.25.1

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

[Cong Wang]

On Mon, Aug 10, 2020 at 3:10 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
>
> 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.
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.

In either case, it does not look like you fix it correctly.

Thanks.
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Re: [Linux-kernel-mentees] [PATCH net] ipvs: Fix uninit-value in do_ip_vs_set_ctl()

[Peilin Ye]

On Mon, Aug 10, 2020 at 08:57:19PM -0700, Cong Wang wrote:
> On Mon, Aug 10, 2020 at 3:10 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
> >
> > 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.

> 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?

@@ -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:

Thank you,
Peilin Ye

> In either case, it does not look like you fix it correctly.
> 
> Thanks.
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Re: [Linux-kernel-mentees] [PATCH net] ipvs: Fix uninit-value in do_ip_vs_set_ctl()

[Julian Anastasov]

	Hello,

On Tue, 11 Aug 2020, Peilin Ye wrote:

> On Mon, Aug 10, 2020 at 08:57:19PM -0700, Cong Wang wrote:
> > On Mon, Aug 10, 2020 at 3:10 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
> > >
> > > 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.
> 
> > 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 :)

> @@ -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 <ja@ssi.bg>
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Re: [Linux-kernel-mentees] [PATCH net] ipvs: Fix uninit-value in do_ip_vs_set_ctl()

[Peilin Ye]

On Tue, Aug 11, 2020 at 09:58:46AM +0300, Julian Anastasov wrote:
> 
> 	Hello,
> 
> On Tue, 11 Aug 2020, Peilin Ye wrote:
> 
> > On Mon, Aug 10, 2020 at 08:57:19PM -0700, Cong Wang wrote:
> > > On Mon, Aug 10, 2020 at 3:10 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
> > > >
> > > > 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.
> > 
> > > 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.

I see, I'll target net-next instead.

> 	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 :)

Ah, this seems much cleaner. I'll send v2 soon, thank you!

Peilin Ye

> > @@ -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 <ja@ssi.bg>
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[Linux-kernel-mentees] [PATCH net-next v2] ipvs: Fix uninit-value in do_ip_vs_set_ctl()

[Peilin Ye]

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

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

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

[Julian Anastasov]

	Hello,

On Tue, 11 Aug 2020, Peilin Ye wrote:

> do_ip_vs_set_ctl() is referencing uninitialized stack value when `len` is
> zero. Fix it.
> 
> Reported-by: syzbot+23b5f9e7caf61d9a3898@syzkaller.appspotmail.com
> Link: https://syzkaller.appspot.com/bug?id=46ebfb92a8a812621a001ef04d90dfa459520fe2
> Suggested-by: Julian Anastasov <ja@ssi.bg>
> Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>

	Looks good to me, thanks!

Acked-by: Julian Anastasov <ja@ssi.bg>

> ---
> Changes in v2:
>     - Target net-next tree. (Suggested by Julian Anastasov <ja@ssi.bg>)
>     - Reject all `len == 0` requests except `IP_VS_SO_SET_FLUSH`, instead
>       of initializing `arg`. (Suggested by Cong Wang
>       <xiyou.wangcong@gmail.com>, Julian Anastasov <ja@ssi.bg>)
> 
>  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

Regards

--
Julian Anastasov <ja@ssi.bg>
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Re: [Linux-kernel-mentees] [PATCH net-next v2] ipvs: Fix uninit-value in do_ip_vs_set_ctl()

[Simon Horman]

On Tue, Aug 11, 2020 at 01:29:04PM +0300, Julian Anastasov wrote:
> 
> 	Hello,
> 
> On Tue, 11 Aug 2020, Peilin Ye wrote:
> 
> > do_ip_vs_set_ctl() is referencing uninitialized stack value when `len` is
> > zero. Fix it.
> > 
> > Reported-by: syzbot+23b5f9e7caf61d9a3898@syzkaller.appspotmail.com
> > Link: https://syzkaller.appspot.com/bug?id=46ebfb92a8a812621a001ef04d90dfa459520fe2
> > Suggested-by: Julian Anastasov <ja@ssi.bg>
> > Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
> 
> 	Looks good to me, thanks!
> 
> Acked-by: Julian Anastasov <ja@ssi.bg>

Pablo, could you consider this for nf-next or should we repost when
net-next re-opens?

Reviewed-by: Simon Horman <horms@verge.net.au>

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

[Pablo Neira Ayuso]

On Tue, Aug 11, 2020 at 02:59:59PM +0200, Simon Horman wrote:
> On Tue, Aug 11, 2020 at 01:29:04PM +0300, Julian Anastasov wrote:
> > 
> > 	Hello,
> > 
> > On Tue, 11 Aug 2020, Peilin Ye wrote:
> > 
> > > do_ip_vs_set_ctl() is referencing uninitialized stack value when `len` is
> > > zero. Fix it.
> > > 
> > > Reported-by: syzbot+23b5f9e7caf61d9a3898@syzkaller.appspotmail.com
> > > Link: https://syzkaller.appspot.com/bug?id=46ebfb92a8a812621a001ef04d90dfa459520fe2
> > > Suggested-by: Julian Anastasov <ja@ssi.bg>
> > > Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
> > 
> > 	Looks good to me, thanks!
> > 
> > Acked-by: Julian Anastasov <ja@ssi.bg>
> 
> Pablo, could you consider this for nf-next or should we repost when
> net-next re-opens?

No worries, it will sit in netfilter's patchwork until net-next
reopens.
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Re: [Linux-kernel-mentees] [PATCH net-next v2] ipvs: Fix uninit-value in do_ip_vs_set_ctl()

[Pablo Neira Ayuso]

On Tue, Aug 11, 2020 at 03:46:40AM -0400, Peilin Ye wrote:
> do_ip_vs_set_ctl() is referencing uninitialized stack value when `len` is
> zero. Fix it.

Applied to nf-next, thanks.
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