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Message-ID: <1568861888-34045-2-git-send-email-nixiaoming@huawei.com>
Date: Thu, 19 Sep 2019 10:58:06 +0800
From: Xiaoming Ni <nixiaoming@...wei.com>
To: <gregkh@...uxfoundation.org>, <akpm@...ux-foundation.org>,
<vvs@...tuozzo.com>, <torvalds@...ux-foundation.org>,
<adobriyan@...il.com>, <anna.schumaker@...app.com>,
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<jlayton@...nel.org>, <luto@...nel.org>, <mingo@...nel.org>,
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<tglx@...utronix.de>, <trond.myklebust@...merspace.com>,
<viresh.kumar@...aro.org>
CC: <stable@...nel.org>, <dylix.dailei@...wei.com>,
<nixiaoming@...wei.com>, <yuehaibing@...wei.com>,
<linux-kernel@...r.kernel.org>, <linux-nfs@...r.kernel.org>,
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Subject: [PATCH v4 1/3] kernel/notifier.c: intercepting duplicate registrations to avoid infinite loops
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@...wei.com>
Reviewed-by: Vasily Averin <vvs@...tuozzo.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
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