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 <[email protected]>
Reviewed-by: Vasily Averin <[email protected]>
---
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
On Thu, Sep 19, 2019 at 10:58:06AM +0800, Xiaoming Ni wrote:
> 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 <[email protected]>
> Reviewed-by: Vasily Averin <[email protected]>
> ---
> kernel/notifier.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
<formletter>
This is not the correct way to submit patches for inclusion in the
stable kernel tree. Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.
</formletter>
Same thing goes for all of the patches in this series.
thanks,
greg k-h
On 2019/9/19 14:36, Greg KH wrote:
> On Thu, Sep 19, 2019 at 10:58:06AM +0800, Xiaoming Ni wrote:
>> 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 <[email protected]>
>> Reviewed-by: Vasily Averin <[email protected]>
>> ---
>> kernel/notifier.c | 5 ++++-
>> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> <formletter>
>
> This is not the correct way to submit patches for inclusion in the
> stable kernel tree. Please read:
> https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
> for how to do this properly.
>
thanks for your guidance
I thought that as long as the code exists in the stable branch, it should be copied to [email protected]
it is my mistake,
These patches are intended to be sent to the main line.
Should I resend it again?
> </formletter>
>
> Same thing goes for all of the patches in this series.
>
> thanks,
>
> greg k-h
>
> .
>
thanks
Xiaoming Ni