From: Xiaoming Ni <nixiaoming@huawei.com>
To: <gregkh@linuxfoundation.org>, <akpm@linux-foundation.org>,
<vvs@virtuozzo.com>, <torvalds@linux-foundation.org>,
<adobriyan@gmail.com>, <anna.schumaker@netapp.com>,
<arjan@linux.intel.com>, <bfields@fieldses.org>,
<chuck.lever@oracle.com>, <davem@davemloft.net>,
<jlayton@kernel.org>, <luto@kernel.org>, <mingo@kernel.org>,
<Nadia.Derbey@bull.net>, <paulmck@linux.vnet.ibm.com>,
<semen.protsenko@linaro.org>, <stern@rowland.harvard.edu>,
<tglx@linutronix.de>, <trond.myklebust@hammerspace.com>,
<viresh.kumar@linaro.org>
Cc: <stable@kernel.org>, <dylix.dailei@huawei.com>,
<nixiaoming@huawei.com>, <yuehaibing@huawei.com>,
<linux-kernel@vger.kernel.org>, <linux-nfs@vger.kernel.org>,
<netdev@vger.kernel.org>
Subject: [PATCH v4 1/3] kernel/notifier.c: intercepting duplicate registrations to avoid infinite loops
Date: Thu, 19 Sep 2019 10:58:06 +0800 [thread overview]
Message-ID: <1568861888-34045-2-git-send-email-nixiaoming@huawei.com> (raw)
In-Reply-To: <1568861888-34045-1-git-send-email-nixiaoming@huawei.com>
Registering the same notifier to a hook repeatedly can cause the hook
list to form a ring or lose other members of the list.
case1: An infinite loop in notifier_chain_register() can cause soft lockup
atomic_notifier_chain_register(&test_notifier_list, &test1);
atomic_notifier_chain_register(&test_notifier_list, &test1);
atomic_notifier_chain_register(&test_notifier_list, &test2);
case2: An infinite loop in notifier_chain_register() can cause soft lockup
atomic_notifier_chain_register(&test_notifier_list, &test1);
atomic_notifier_chain_register(&test_notifier_list, &test1);
atomic_notifier_call_chain(&test_notifier_list, 0, NULL);
case3: lose other hook test2
atomic_notifier_chain_register(&test_notifier_list, &test1);
atomic_notifier_chain_register(&test_notifier_list, &test2);
atomic_notifier_chain_register(&test_notifier_list, &test1);
case4: Unregister returns 0, but the hook is still in the linked list,
and it is not really registered. If you call notifier_call_chain
after ko is unloaded, it will trigger oops.
If the system is configured with softlockup_panic and the same
hook is repeatedly registered on the panic_notifier_list, it
will cause a loop panic.
Add a check in notifier_chain_register(),
Intercepting duplicate registrations to avoid infinite loops
Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
Reviewed-by: Vasily Averin <vvs@virtuozzo.com>
---
kernel/notifier.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/notifier.c b/kernel/notifier.c
index d9f5081..30bedb8 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -23,7 +23,10 @@ static int notifier_chain_register(struct notifier_block **nl,
struct notifier_block *n)
{
while ((*nl) != NULL) {
- WARN_ONCE(((*nl) == n), "double register detected");
+ if (unlikely((*nl) == n)) {
+ WARN(1, "double register detected");
+ return 0;
+ }
if (n->priority > (*nl)->priority)
break;
nl = &((*nl)->next);
--
1.8.5.6
next prev parent reply other threads:[~2019-09-19 2:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-19 2:58 [PATCH v4 0/3] kernel/notifier.c: intercepting duplicate registrations to avoid infinite loops Xiaoming Ni
2019-09-19 2:58 ` Xiaoming Ni [this message]
2019-09-19 6:36 ` [PATCH v4 1/3] " Greg KH
2019-09-19 12:55 ` Xiaoming Ni
2019-09-19 2:58 ` [PATCH v4 2/3] kernel/notifier.c: remove notifier_chain_cond_register() Xiaoming Ni
2019-09-19 2:58 ` [PATCH v4 3/3] kernel/notifier.c: remove blocking_notifier_chain_cond_register() Xiaoming Ni
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