From: Xiaoming Ni <nixiaom...@huawei.com>
[ Upstream commit 1a50cb80f219c44adb6265f5071b81fc3c1deced ]
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
Link:
http://lkml.kernel.org/r/1568861888-34045-2-git-send-email-nixiaom...@huawei.com
Signed-off-by: Xiaoming Ni <nixiaom...@huawei.com>
Reviewed-by: Vasily Averin <v...@virtuozzo.com>
Reviewed-by: Andrew Morton <a...@linux-foundation.org>
Cc: Alexey Dobriyan <adobri...@gmail.com>
Cc: Anna Schumaker <anna.schuma...@netapp.com>
Cc: Arjan van de Ven <ar...@linux.intel.com>
Cc: J. Bruce Fields <bfie...@fieldses.org>
Cc: Chuck Lever <chuck.le...@oracle.com>
Cc: David S. Miller <da...@davemloft.net>
Cc: Jeff Layton <jlay...@kernel.org>
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Nadia Derbey <nadia.der...@bull.net>
Cc: "Paul E. McKenney" <paul...@kernel.org>
Cc: Sam Protsenko <semen.protse...@linaro.org>
Cc: Alan Stern <st...@rowland.harvard.edu>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Trond Myklebust <trond.mykleb...@hammerspace.com>
Cc: Viresh Kumar <viresh.ku...@linaro.org>
Cc: Xiaoming Ni <nixiaom...@huawei.com>
Cc: YueHaibing <yuehaib...@huawei.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
kernel/notifier.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/notifier.c b/kernel/notifier.c
index 157d7c29f7207..f6d5ffe4e72ec 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);
--
2.25.1
