From: Mahesh Jagannath Salgaonkar <mahesh@linux.ibm.com>
To: ananth@linux.ibm.com, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2] powernv/elog: Fix the race while processing OPAL error log event.
Date: Tue, 6 Oct 2020 10:41:32 +0530 [thread overview]
Message-ID: <5a4a6e03-b2ae-5702-89ca-6656606c7a5e@linux.ibm.com> (raw)
In-Reply-To: <df7cebd0-bec3-d716-5514-61c4043a6d30@linux.ibm.com>
On 10/5/20 4:17 PM, Ananth N Mavinakayanahalli wrote:
> On 10/5/20 9:42 AM, Mahesh Salgaonkar wrote:
>> Every error log reported by OPAL is exported to userspace through a sysfs
>> interface and notified using kobject_uevent(). The userspace daemon
>> (opal_errd) then reads the error log and acknowledges it error log is
>> saved
>> safely to disk. Once acknowledged the kernel removes the respective sysfs
>> file entry causing respective resources getting released including
>> kobject.
>>
>> However there are chances where user daemon may already be scanning elog
>> entries while new sysfs elog entry is being created by kernel. User
>> daemon
>> may read this new entry and ack it even before kernel can notify
>> userspace
>> about it through kobject_uevent() call. If that happens then we have a
>> potential race between elog_ack_store->kobject_put() and kobject_uevent
>> which can lead to use-after-free issue of a kernfs object resulting
>> into a
>> kernel crash. This patch fixes this race by protecting a sysfs file
>> creation/notification by holding an additional reference count on kobject
>> until we safely send kobject_uevent().
>>
>> Reported-by: Oliver O'Halloran <oohall@gmail.com>
>> Signed-off-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
>
> cc stable?
>
Will add it in v3.
Thanks,
-Mahesh.
next prev parent reply other threads:[~2020-10-06 5:14 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-05 4:12 [PATCH v2] powernv/elog: Fix the race while processing OPAL error log event Mahesh Salgaonkar
2020-10-05 10:47 ` Ananth N Mavinakayanahalli
2020-10-06 0:22 ` Oliver O'Halloran
2020-10-06 5:11 ` Mahesh Jagannath Salgaonkar [this message]
2020-10-06 0:25 ` Oliver O'Halloran
2020-10-06 2:26 ` Vasant Hegde
2020-10-06 4:48 ` Mahesh Jagannath Salgaonkar
2020-10-06 5:40 ` Michael Ellerman
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