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race of lockd inetaddr notifiers vs nlmsvc_rqst change 

[ Upstream commit 6b18dd1c03 ]

lockd_inet[6]addr_event use nlmsvc_rqst without taken nlmsvc_mutex,
nlmsvc_rqst can be changed during execution of notifiers and crash the host.

Patch enables access to nlmsvc_rqst only when it was correctly initialized
and delays its cleanup until notifiers are no longer in use.

Note that nlmsvc_rqst can be temporally set to ERR_PTR, so the "if
(nlmsvc_rqst)" check in notifiers is insufficient on its own.

Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Tested-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
pull/10/head
Vasily Averin 2017-11-10 10:19:26 +03:00 committed by Greg Kroah-Hartman
parent 631db7f389
commit 156c80d4e1
1 changed files with 14 additions and 2 deletions
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16
fs/lockd/svc.c
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@ -57,6 +57,9 @@ static struct task_struct *nlmsvc_task;
static struct svc_rqst *nlmsvc_rqst;
unsigned long nlmsvc_timeout;
atomic_t nlm_ntf_refcnt = ATOMIC_INIT(0);
DECLARE_WAIT_QUEUE_HEAD(nlm_ntf_wq);
unsigned int lockd_net_id;
/*
@ -292,7 +295,8 @@ static int lockd_inetaddr_event(struct notifier_block *this,
struct in_ifaddr *ifa = (struct in_ifaddr *)ptr;
struct sockaddr_in sin;
if (event != NETDEV_DOWN)
if ((event != NETDEV_DOWN) ||
!atomic_inc_not_zero(&nlm_ntf_refcnt))
goto out;
if (nlmsvc_rqst) {
@ -303,6 +307,8 @@ static int lockd_inetaddr_event(struct notifier_block *this,
svc_age_temp_xprts_now(nlmsvc_rqst->rq_server,
(struct sockaddr *)&sin);
}
atomic_dec(&nlm_ntf_refcnt);
wake_up(&nlm_ntf_wq);
out:
return NOTIFY_DONE;
@ -319,7 +325,8 @@ static int lockd_inet6addr_event(struct notifier_block *this,
struct inet6_ifaddr *ifa = (struct inet6_ifaddr *)ptr;
struct sockaddr_in6 sin6;
if (event != NETDEV_DOWN)
if ((event != NETDEV_DOWN) ||
!atomic_inc_not_zero(&nlm_ntf_refcnt))
goto out;
if (nlmsvc_rqst) {
@ -331,6 +338,8 @@ static int lockd_inet6addr_event(struct notifier_block *this,
svc_age_temp_xprts_now(nlmsvc_rqst->rq_server,
(struct sockaddr *)&sin6);
}
atomic_dec(&nlm_ntf_refcnt);
wake_up(&nlm_ntf_wq);
out:
return NOTIFY_DONE;
@ -347,10 +356,12 @@ static void lockd_unregister_notifiers(void)
#if IS_ENABLED(CONFIG_IPV6)
unregister_inet6addr_notifier(&lockd_inet6addr_notifier);
#endif
wait_event(nlm_ntf_wq, atomic_read(&nlm_ntf_refcnt) == 0);
}
static void lockd_svc_exit_thread(void)
{
atomic_dec(&nlm_ntf_refcnt);
lockd_unregister_notifiers();
svc_exit_thread(nlmsvc_rqst);
}
@ -375,6 +386,7 @@ static int lockd_start_svc(struct svc_serv *serv)
goto out_rqst;
}
atomic_inc(&nlm_ntf_refcnt);
svc_sock_update_bufs(serv);
serv->sv_maxconn = nlm_max_connections;