* [PATCH v3 1/3] kernel/notifier.c: avoid duplicate registration
@ 2019-07-10 3:09 Xiaoming Ni
2019-07-17 11:19 ` Vasily Averin
0 siblings, 1 reply; 2+ messages in thread
From: Xiaoming Ni @ 2019-07-10 3:09 UTC (permalink / raw)
To: adobriyan, akpm, anna.schumaker, arjan, bfields, chuck.lever,
davem, gregkh, jlayton, luto, mingo, Nadia.Derbey, paulmck,
semen.protsenko, stable, stern, tglx, torvalds, trond.myklebust,
viresh.kumar, vvs
Cc: alex.huangjianhui, dylix.dailei, nixiaoming, linux-kernel,
linux-nfs, netdev
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() to avoid duplicate registration
Signed-off-by: Xiaoming Ni <nixiaoming@huawei.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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v3 1/3] kernel/notifier.c: avoid duplicate registration
2019-07-10 3:09 [PATCH v3 1/3] kernel/notifier.c: avoid duplicate registration Xiaoming Ni
@ 2019-07-17 11:19 ` Vasily Averin
0 siblings, 0 replies; 2+ messages in thread
From: Vasily Averin @ 2019-07-17 11:19 UTC (permalink / raw)
To: Xiaoming Ni, adobriyan, akpm, anna.schumaker, arjan, bfields,
chuck.lever, davem, gregkh, jlayton, luto, mingo, Nadia.Derbey,
paulmck, semen.protsenko, stable, stern, tglx, torvalds,
trond.myklebust, viresh.kumar
Cc: alex.huangjianhui, dylix.dailei, linux-kernel, linux-nfs, netdev
On 7/10/19 6:09 AM, 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() to avoid duplicate registration
>
> 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);
>
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2019-07-17 11:19 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-07-10 3:09 [PATCH v3 1/3] kernel/notifier.c: avoid duplicate registration Xiaoming Ni
2019-07-17 11:19 ` Vasily Averin
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).