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authorVasily Averin <vvs@virtuozzo.com>2016-09-21 15:33:05 +0300
committerJ. Bruce Fields <bfields@redhat.com>2016-09-26 14:17:45 -0400
commit1eca45f8a840987d0df355e0176921653e4f7ec2 (patch)
tree7aad7b543bc8b14607968c78429478375dde02ce /fs/nfsd
parent25d55296dd3eac23adb2ae46b67b65bf73b22fb2 (diff)
downloadlinux-1eca45f8a840987d0df355e0176921653e4f7ec2.tar.bz2
NFSD: fix corruption in notifier registration
By design notifier can be registered once only, however nfsd registers the same inetaddr notifiers per net-namespace. When this happen it corrupts list of notifiers, as result some notifiers can be not called on proper event, traverse on list can be cycled forever, and second unregister can access already freed memory. Cc: stable@vger.kernel.org fixes: 36684996 ("nfsd: Register callbacks on the inetaddr_chain and inet6addr_chain") Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Reviewed-by: Jeff Layton <jlayton@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Diffstat (limited to 'fs/nfsd')
-rw-r--r--fs/nfsd/nfssvc.c18
1 files changed, 14 insertions, 4 deletions
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 45007acaf364..a2b65fc56dd6 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -366,14 +366,21 @@ static struct notifier_block nfsd_inet6addr_notifier = {
};
#endif
+/* Only used under nfsd_mutex, so this atomic may be overkill: */
+static atomic_t nfsd_notifier_refcount = ATOMIC_INIT(0);
+
static void nfsd_last_thread(struct svc_serv *serv, struct net *net)
{
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
- unregister_inetaddr_notifier(&nfsd_inetaddr_notifier);
+ /* check if the notifier still has clients */
+ if (atomic_dec_return(&nfsd_notifier_refcount) == 0) {
+ unregister_inetaddr_notifier(&nfsd_inetaddr_notifier);
#if IS_ENABLED(CONFIG_IPV6)
- unregister_inet6addr_notifier(&nfsd_inet6addr_notifier);
+ unregister_inet6addr_notifier(&nfsd_inet6addr_notifier);
#endif
+ }
+
/*
* write_ports can create the server without actually starting
* any threads--if we get shut down before any threads are
@@ -488,10 +495,13 @@ int nfsd_create_serv(struct net *net)
}
set_max_drc();
- register_inetaddr_notifier(&nfsd_inetaddr_notifier);
+ /* check if the notifier is already set */
+ if (atomic_inc_return(&nfsd_notifier_refcount) == 1) {
+ register_inetaddr_notifier(&nfsd_inetaddr_notifier);
#if IS_ENABLED(CONFIG_IPV6)
- register_inet6addr_notifier(&nfsd_inet6addr_notifier);
+ register_inet6addr_notifier(&nfsd_inet6addr_notifier);
#endif
+ }
do_gettimeofday(&nn->nfssvc_boot); /* record boot time */
return 0;
}