From: Xiaoming Ni <nixiaoming@xxxxxxxxxx>
Subject: kernel/notifier.c: intercept 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
Link: http://lkml.kernel.org/r/1568861888-34045-2-git-send-email-nixiaoming@xxxxxxxxxx
Signed-off-by: Xiaoming Ni <nixiaoming@xxxxxxxxxx>
Reviewed-by: Vasily Averin <vvs@xxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Anna Schumaker <anna.schumaker@xxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: J. Bruce Fields <bfields@xxxxxxxxxxxx>
Cc: Chuck Lever <chuck.lever@xxxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Jeff Layton <jlayton@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Nadia Derbey <Nadia.Derbey@xxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Sam Protsenko <semen.protsenko@xxxxxxxxxx>
Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Cc: Xiaoming Ni <nixiaoming@xxxxxxxxxx>
Cc: YueHaibing <yuehaibing@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/notifier.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/kernel/notifier.c~kernel-notifierc-intercepting-duplicate-registrations-to-avoid-infinite-loops
+++ a/kernel/notifier.c
@@ -23,7 +23,10 @@ static int notifier_chain_register(struc
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);
_
