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authorNeil Horman <nhorman@tuxdriver.com>2007-09-11 11:28:26 +0200
committerDavid S. Miller <davem@davemloft.net>2007-09-11 11:28:26 +0200
commit16fcec35e7d7c4faaa4709f6434a4a25b06d25e3 (patch)
tree5febf4d688f2c32ed55e02bc20246388b74d85e4
parent0fb96701376874c9f1f80322f89a5bf4457c709f (diff)
[NETFILTER]: Fix/improve deadlock condition on module removal netfilter
So I've had a deadlock reported to me. I've found that the sequence of events goes like this: 1) process A (modprobe) runs to remove ip_tables.ko 2) process B (iptables-restore) runs and calls setsockopt on a netfilter socket, increasing the ip_tables socket_ops use count 3) process A acquires a file lock on the file ip_tables.ko, calls remove_module in the kernel, which in turn executes the ip_tables module cleanup routine, which calls nf_unregister_sockopt 4) nf_unregister_sockopt, seeing that the use count is non-zero, puts the calling process into uninterruptible sleep, expecting the process using the socket option code to wake it up when it exits the kernel 4) the user of the socket option code (process B) in do_ipt_get_ctl, calls ipt_find_table_lock, which in this case calls request_module to load ip_tables_nat.ko 5) request_module forks a copy of modprobe (process C) to load the module and blocks until modprobe exits. 6) Process C. forked by request_module process the dependencies of ip_tables_nat.ko, of which ip_tables.ko is one. 7) Process C attempts to lock the request module and all its dependencies, it blocks when it attempts to lock ip_tables.ko (which was previously locked in step 3) Theres not really any great permanent solution to this that I can see, but I've developed a two part solution that corrects the problem Part 1) Modifies the nf_sockopt registration code so that, instead of using a use counter internal to the nf_sockopt_ops structure, we instead use a pointer to the registering modules owner to do module reference counting when nf_sockopt calls a modules set/get routine. This prevents the deadlock by preventing set 4 from happening. Part 2) Enhances the modprobe utilty so that by default it preforms non-blocking remove operations (the same way rmmod does), and add an option to explicity request blocking operation. So if you select blocking operation in modprobe you can still cause the above deadlock, but only if you explicity try (and since root can do any old stupid thing it would like.... :) ). Signed-off-by: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/linux/netfilter.h5
-rw-r--r--net/bridge/netfilter/ebtables.c1
-rw-r--r--net/ipv4/ipvs/ip_vs_ctl.c1
-rw-r--r--net/ipv4/netfilter/arp_tables.c1
-rw-r--r--net/ipv4/netfilter/ip_tables.c1
-rw-r--r--net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c1
-rw-r--r--net/ipv6/netfilter/ip6_tables.c1
-rw-r--r--net/netfilter/nf_sockopt.c36
8 files changed, 19 insertions, 28 deletions
diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index 0eed0b7ab2d..1dd075eda59 100644
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -88,9 +88,8 @@ struct nf_sockopt_ops
int (*compat_get)(struct sock *sk, int optval,
void __user *user, int *len);
- /* Number of users inside set() or get(). */
- unsigned int use;
- struct task_struct *cleanup_task;
+ /* Use the module struct to lock set/get code in place */
+ struct module *owner;
};
/* Each queued (to userspace) skbuff has one of these. */
diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 4169a2a89a3..6018d0e5193 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1513,6 +1513,7 @@ static struct nf_sockopt_ops ebt_sockopts =
.get_optmin = EBT_BASE_CTL,
.get_optmax = EBT_SO_GET_MAX + 1,
.get = do_ebt_get_ctl,
+ .owner = THIS_MODULE,
};
static int __init ebtables_init(void)
diff --git a/net/ipv4/ipvs/ip_vs_ctl.c b/net/ipv4/ipvs/ip_vs_ctl.c
index 902fd578aa3..f656d41d8d4 100644
--- a/net/ipv4/ipvs/ip_vs_ctl.c
+++ b/net/ipv4/ipvs/ip_vs_ctl.c
@@ -2339,6 +2339,7 @@ static struct nf_sockopt_ops ip_vs_sockopts = {
.get_optmin = IP_VS_BASE_CTL,
.get_optmax = IP_VS_SO_GET_MAX+1,
.get = do_ip_vs_get_ctl,
+ .owner = THIS_MODULE,
};
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index d1149aba935..29114a9ccd1 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -1161,6 +1161,7 @@ static struct nf_sockopt_ops arpt_sockopts = {
.get_optmin = ARPT_BASE_CTL,
.get_optmax = ARPT_SO_GET_MAX+1,
.get = do_arpt_get_ctl,
+ .owner = THIS_MODULE,
};
static int __init arp_tables_init(void)
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index e1b402c6b85..6486894f450 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -2296,6 +2296,7 @@ static struct nf_sockopt_ops ipt_sockopts = {
#ifdef CONFIG_COMPAT
.compat_get = compat_do_ipt_get_ctl,
#endif
+ .owner = THIS_MODULE,
};
static struct xt_match icmp_matchstruct __read_mostly = {
diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
index 53cb1772f38..f813e02aab3 100644
--- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
+++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
@@ -399,6 +399,7 @@ static struct nf_sockopt_ops so_getorigdst = {
.get_optmin = SO_ORIGINAL_DST,
.get_optmax = SO_ORIGINAL_DST+1,
.get = &getorigdst,
+ .owner = THIS_MODULE,
};
struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4 __read_mostly = {
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index aeda617246b..cd9df02bb85 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -1462,6 +1462,7 @@ static struct nf_sockopt_ops ip6t_sockopts = {
.get_optmin = IP6T_BASE_CTL,
.get_optmax = IP6T_SO_GET_MAX+1,
.get = do_ip6t_get_ctl,
+ .owner = THIS_MODULE,
};
static struct xt_match icmp6_matchstruct __read_mostly = {
diff --git a/net/netfilter/nf_sockopt.c b/net/netfilter/nf_sockopt.c
index 8b8ece75031..e32761ce260 100644
--- a/net/netfilter/nf_sockopt.c
+++ b/net/netfilter/nf_sockopt.c
@@ -55,18 +55,7 @@ EXPORT_SYMBOL(nf_register_sockopt);
void nf_unregister_sockopt(struct nf_sockopt_ops *reg)
{
- /* No point being interruptible: we're probably in cleanup_module() */
- restart:
mutex_lock(&nf_sockopt_mutex);
- if (reg->use != 0) {
- /* To be woken by nf_sockopt call... */
- /* FIXME: Stuart Young's name appears gratuitously. */
- set_current_state(TASK_UNINTERRUPTIBLE);
- reg->cleanup_task = current;
- mutex_unlock(&nf_sockopt_mutex);
- schedule();
- goto restart;
- }
list_del(&reg->list);
mutex_unlock(&nf_sockopt_mutex);
}
@@ -86,10 +75,11 @@ static int nf_sockopt(struct sock *sk, int pf, int val,
list_for_each(i, &nf_sockopts) {
ops = (struct nf_sockopt_ops *)i;
if (ops->pf == pf) {
+ if (!try_module_get(ops->owner))
+ goto out_nosup;
if (get) {
if (val >= ops->get_optmin
&& val < ops->get_optmax) {
- ops->use++;
mutex_unlock(&nf_sockopt_mutex);
ret = ops->get(sk, val, opt, len);
goto out;
@@ -97,23 +87,20 @@ static int nf_sockopt(struct sock *sk, int pf, int val,
} else {
if (val >= ops->set_optmin
&& val < ops->set_optmax) {
- ops->use++;
mutex_unlock(&nf_sockopt_mutex);
ret = ops->set(sk, val, opt, *len);
goto out;
}
}
+ module_put(ops->owner);
}
}
+ out_nosup:
mutex_unlock(&nf_sockopt_mutex);
return -ENOPROTOOPT;
out:
- mutex_lock(&nf_sockopt_mutex);
- ops->use--;
- if (ops->cleanup_task)
- wake_up_process(ops->cleanup_task);
- mutex_unlock(&nf_sockopt_mutex);
+ module_put(ops->owner);
return ret;
}
@@ -144,10 +131,12 @@ static int compat_nf_sockopt(struct sock *sk, int pf, int val,
list_for_each(i, &nf_sockopts) {
ops = (struct nf_sockopt_ops *)i;
if (ops->pf == pf) {
+ if (!try_module_get(ops->owner))
+ goto out_nosup;
+
if (get) {
if (val >= ops->get_optmin
&& val < ops->get_optmax) {
- ops->use++;
mutex_unlock(&nf_sockopt_mutex);
if (ops->compat_get)
ret = ops->compat_get(sk,
@@ -160,7 +149,6 @@ static int compat_nf_sockopt(struct sock *sk, int pf, int val,
} else {
if (val >= ops->set_optmin
&& val < ops->set_optmax) {
- ops->use++;
mutex_unlock(&nf_sockopt_mutex);
if (ops->compat_set)
ret = ops->compat_set(sk,
@@ -171,17 +159,15 @@ static int compat_nf_sockopt(struct sock *sk, int pf, int val,
goto out;
}
}
+ module_put(ops->owner);
}
}
+ out_nosup:
mutex_unlock(&nf_sockopt_mutex);
return -ENOPROTOOPT;
out:
- mutex_lock(&nf_sockopt_mutex);
- ops->use--;
- if (ops->cleanup_task)
- wake_up_process(ops->cleanup_task);
- mutex_unlock(&nf_sockopt_mutex);
+ module_put(ops->owner);
return ret;
}