3.0-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <eduma...@google.com>
[ Upstream commit 6d772ac5578f711d1ce7b03535d1c95bffb21dff ]
On some suspend/resume operations involving wimax device, we have
noticed some intermittent memory corruptions in netlink code.
Stéphane Marchesin tracked this corruption in netlink_update_listeners()
and suggested a patch.
It appears netlink_release() should use kfree_rcu() instead of kfree()
for the listeners structure as it may be used by other cpus using RCU
protection.
netlink_release() must set to NULL the listeners pointer when
it is about to be freed.
Also have to protect netlink_update_listeners() and
netlink_has_listeners() if listeners is NULL.
Add a nl_deref_protected() lockdep helper to properly document which
locks protects us.
Reported-by: Jonathan Kliegman <kli...@google.com>
Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Stéphane Marchesin <marc...@google.com>
Cc: Sam Leffler <sleff...@google.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
net/netlink/af_netlink.c | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -137,6 +137,8 @@ static void netlink_destroy_callback(str
static DEFINE_RWLOCK(nl_table_lock);
static atomic_t nl_table_users = ATOMIC_INIT(0);
+#define nl_deref_protected(X) rcu_dereference_protected(X,
lockdep_is_held(&nl_table_lock));
+
static ATOMIC_NOTIFIER_HEAD(netlink_chain);
static u32 netlink_group_mask(u32 group)
@@ -331,6 +333,11 @@ netlink_update_listeners(struct sock *sk
struct hlist_node *node;
unsigned long mask;
unsigned int i;
+ struct listeners *listeners;
+
+ listeners = nl_deref_protected(tbl->listeners);
+ if (!listeners)
+ return;
for (i = 0; i < NLGRPLONGS(tbl->groups); i++) {
mask = 0;
@@ -338,7 +345,7 @@ netlink_update_listeners(struct sock *sk
if (i < NLGRPLONGS(nlk_sk(sk)->ngroups))
mask |= nlk_sk(sk)->groups[i];
}
- tbl->listeners->masks[i] = mask;
+ listeners->masks[i] = mask;
}
/* this function is only called with the netlink table "grabbed", which
* makes sure updates are visible before bind or setsockopt return. */
@@ -519,7 +526,11 @@ static int netlink_release(struct socket
if (netlink_is_kernel(sk)) {
BUG_ON(nl_table[sk->sk_protocol].registered == 0);
if (--nl_table[sk->sk_protocol].registered == 0) {
- kfree(nl_table[sk->sk_protocol].listeners);
+ struct listeners *old;
+
+ old =
nl_deref_protected(nl_table[sk->sk_protocol].listeners);
+ RCU_INIT_POINTER(nl_table[sk->sk_protocol].listeners,
NULL);
+ kfree_rcu(old, rcu);
nl_table[sk->sk_protocol].module = NULL;
nl_table[sk->sk_protocol].registered = 0;
}
@@ -950,7 +961,7 @@ int netlink_has_listeners(struct sock *s
rcu_read_lock();
listeners = rcu_dereference(nl_table[sk->sk_protocol].listeners);
- if (group - 1 < nl_table[sk->sk_protocol].groups)
+ if (listeners && group - 1 < nl_table[sk->sk_protocol].groups)
res = test_bit(group - 1, listeners->masks);
rcu_read_unlock();
@@ -1585,7 +1596,7 @@ int __netlink_change_ngroups(struct sock
new = kzalloc(sizeof(*new) + NLGRPSZ(groups), GFP_ATOMIC);
if (!new)
return -ENOMEM;
- old = rcu_dereference_raw(tbl->listeners);
+ old = nl_deref_protected(tbl->listeners);
memcpy(new->masks, old->masks, NLGRPSZ(tbl->groups));
rcu_assign_pointer(tbl->listeners, new);
--
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