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Date: Wed, 25 Nov 2020 18:04:09 +0100 From: Benjamin Block <bblock@...ux.ibm.com> To: Qinglang Miao <miaoqinglang@...wei.com> Cc: Steffen Maier <maier@...ux.ibm.com>, Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ibm.com>, linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org Subject: Re: [PATCH] scsi: zfcp: fix use-after-free in zfcp_sysfs_port_remove_store On Fri, Nov 20, 2020 at 03:48:53PM +0800, Qinglang Miao wrote: > kfree(port) is called in put_device(&port->dev) so that following > use would cause use-after-free bug. > > the former put_device is redundant for device_unregister contains > put_device already. So just remove it to fix this. > > Fixes: 83d4e1c33d93 ("[SCSI] zfcp: cleanup port sysfs attribute usage") > Reported-by: Hulk Robot <hulkci@...wei.com> > Signed-off-by: Qinglang Miao <miaoqinglang@...wei.com> > --- > drivers/s390/scsi/zfcp_sysfs.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/drivers/s390/scsi/zfcp_sysfs.c b/drivers/s390/scsi/zfcp_sysfs.c > index 8d9662e8b..06285e452 100644 > --- a/drivers/s390/scsi/zfcp_sysfs.c > +++ b/drivers/s390/scsi/zfcp_sysfs.c > @@ -327,8 +327,6 @@ static ssize_t zfcp_sysfs_port_remove_store(struct device *dev, > list_del(&port->list); > write_unlock_irq(&adapter->port_list_lock); > > - put_device(&port->dev); > - > zfcp_erp_port_shutdown(port, 0, "syprs_1"); > device_unregister(&port->dev); > out: Hmm, the placement of the put_device() is indeed strange, now that I think about it. But just removing it and then having a dangling reference also seems wrong - we do get one explicitly in `zfcp_get_port_by_wwpn()`. My first thought would be to move it after the `device_unregister()` call, and before the `out:` label. -- Best Regards, Benjamin Block / Linux on IBM Z Kernel Development / IBM Systems IBM Deutschland Research & Development GmbH / https://www.ibm.com/privacy Vorsitz. AufsR.: Gregor Pillen / Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen / Registergericht: AmtsG Stuttgart, HRB 243294
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