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netlink: use kfree_rcu() in netlink_release() 

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 <kliegs@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Stéphane Marchesin <marcheu@google.com>
Cc: Sam Leffler <sleffler@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-10-18 03:21:55 +00:00 committed by David S. Miller
parent 13d82bf50d
commit 6d772ac557
1 changed files with 15 additions and 4 deletions
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19
net/netlink/af_netlink.c
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@ -138,6 +138,8 @@ static int netlink_dump(struct sock *sk);
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 inline u32 netlink_group_mask(u32 group)
@ -345,6 +347,11 @@ 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;
@ -352,7 +359,7 @@ 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. */
@ -536,7 +543,11 @@ static int netlink_release(struct socket *sock)
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].bind = NULL;
nl_table[sk->sk_protocol].flags = 0;
@ -982,7 +993,7 @@ int netlink_has_listeners(struct sock *sk, unsigned int group)
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();
@ -1625,7 +1636,7 @@ int __netlink_change_ngroups(struct sock *sk, unsigned int groups)
new = kzalloc(sizeof(*new) + NLGRPSZ(groups), GFP_ATOMIC);
if (!new)
return -ENOMEM;
old = rcu_dereference_protected(tbl->listeners, 1);
old = nl_deref_protected(tbl->listeners);
memcpy(new->masks, old->masks, NLGRPSZ(tbl->groups));
rcu_assign_pointer(tbl->listeners, new);