2.6.28(.1) and netlink: scheduling while atomic

2.6.28(.1) and netlink: scheduling while atomic

[Kövesdi György]

Hi,

The new netlink interface allows to add NAT directly to a conntrack entry.
If it is used when the moudule nf-nat-ipv4 is not loaded in, it results in 
crash:
BUG: scheduling while atomic
It is in the kernels 2.6.28 and 2.6.28.1 in the function 
ctnetlink_parse_nat_setup(): it calls request_module() which causes the 
problem. If the module is already loaded, then there is no problem.

Regards:
K. Gy.

Re: 2.6.28(.1) and netlink: scheduling while atomic

[Patrick McHardy]

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Kövesdi György wrote:
> The new netlink interface allows to add NAT directly to a conntrack entry.
> If it is used when the moudule nf-nat-ipv4 is not loaded in, it results in 
> crash:
> BUG: scheduling while atomic
> It is in the kernels 2.6.28 and 2.6.28.1 in the function 
> ctnetlink_parse_nat_setup(): it calls request_module() which causes the 
> problem. If the module is already loaded, then there is no problem.


Thanks for the report. Does this patch fix it?

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diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 3dddec6..c32a7e8 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -831,13 +831,16 @@ ctnetlink_parse_nat_setup(struct nf_conn *ct,
 	if (!parse_nat_setup) {
 #ifdef CONFIG_MODULES
 		rcu_read_unlock();
+		spin_unlock_bh(&nf_conntrack_lock);
 		nfnl_unlock();
 		if (request_module("nf-nat-ipv4") < 0) {
 			nfnl_lock();
+			spin_lock_bh(&nf_conntrack_lock);
 			rcu_read_lock();
 			return -EOPNOTSUPP;
 		}
 		nfnl_lock();
+		spin_lock_bh(&nf_conntrack_lock);
 		rcu_read_lock();
 		if (nfnetlink_parse_nat_setup_hook)
 			return -EAGAIN;

Re: 2.6.28(.1) and netlink: scheduling while atomic

[Kövesdi György]

> Thanks for the report. Does this patch fix it?
Thanks, it works!

Regards
K. Gy.

Re: 2.6.28(.1) and netlink: scheduling while atomic

[Pablo Neira Ayuso]

Patrick McHardy wrote:
> Kövesdi György wrote:
>> The new netlink interface allows to add NAT directly to a conntrack
>> entry.
>> If it is used when the moudule nf-nat-ipv4 is not loaded in, it
>> results in crash:
>> BUG: scheduling while atomic
>> It is in the kernels 2.6.28 and 2.6.28.1 in the function
>> ctnetlink_parse_nat_setup(): it calls request_module() which causes
>> the problem. If the module is already loaded, then there is no problem.
> 
> Thanks for the report. Does this patch fix it?

Hm, this was introduced when we fixed the problem with race condition in
the conntrack creation :( It would be worth to pass it to 2.6.29-rc.

-- 
"Los honestos son inadaptados sociales" -- Les Luthiers

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Re: 2.6.28(.1) and netlink: scheduling while atomic

[Patrick McHardy]

Pablo Neira Ayuso wrote:
> Patrick McHardy wrote:
>> Thanks for the report. Does this patch fix it?
> 
> Hm, this was introduced when we fixed the problem with race condition in
> the conntrack creation :( It would be worth to pass it to 2.6.29-rc.

Of course :) I'll also send it to stable once it hits upstream.