Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [ 45/66] netlink: use kfree rcu() in netlink release() | Date | Wed, 14 Nov 2012 20:10:50 -0800 |
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3.6-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet <edumazet@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 <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> Signed-off-by: Greg Kroah-Hartman <gregkh@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 @@ -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 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; } @@ -978,7 +989,7 @@ 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(); @@ -1620,7 +1631,7 @@ int __netlink_change_ngroups(struct sock 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);
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