2020-05-28 02:17:26

by Qiushi Wu

Subject: [PATCH] Fix reference count leak in pci_create_slot

From: Qiushi Wu <[email protected]>

kobject_init_and_add() takes reference even when it fails.
If this function returns an error, kobject_put() must be called to
properly clean up the memory associated with the object. Thus,
when call of kobject_init_and_add() fail, we should call kobject_put()
instead of kfree(). Previous commit "b8eb718348b8" fixed a similar problem.

Fixes: 5fe6cc60680d ("PCI: prevent duplicate slot names")
Signed-off-by: Qiushi Wu <[email protected]>
---
drivers/pci/slot.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
index cc386ef2fa12..3861505741e6 100644
--- a/drivers/pci/slot.c
+++ b/drivers/pci/slot.c
@@ -268,13 +268,16 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
slot_name = make_slot_name(name);
if (!slot_name) {
err = -ENOMEM;
+ kfree(slot);
goto err;
}

err = kobject_init_and_add(&slot->kobj, &pci_slot_ktype, NULL,
"%s", slot_name);
- if (err)
+ if (err) {
+ kobject_put(&slot->kobj);
goto err;
+ }

INIT_LIST_HEAD(&slot->list);
list_add(&slot->list, &parent->slots);
@@ -293,7 +296,6 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
mutex_unlock(&pci_slot_mutex);
return slot;
err:
- kfree(slot);
slot = ERR_PTR(err);
goto out;
}
--
2.17.1

2020-07-10 21:05:26

by Bjorn Helgaas

Subject: Re: [PATCH] Fix reference count leak in pci_create_slot

On Wed, May 27, 2020 at 09:13:22PM -0500, [email protected] wrote:
> From: Qiushi Wu <[email protected]>
>
> kobject_init_and_add() takes reference even when it fails.
> If this function returns an error, kobject_put() must be called to
> properly clean up the memory associated with the object. Thus,
> when call of kobject_init_and_add() fail, we should call kobject_put()
> instead of kfree(). Previous commit "b8eb718348b8" fixed a similar problem.

Looks like you are also checking other kobject_init_and_add() callers?
I see some similar messages on linux-kernel. Thanks for doing that!

I looked at the first dozen or so callers and the following look
broken and I don't see patches for them (yet):

cache_add_dev()
sq_dev_add
blk_integrity_add
acpi_expose_nondev_subnodes
rnbd_clt_add_dev_kobj

> Fixes: 5fe6cc60680d ("PCI: prevent duplicate slot names")

I'm not sure this is correct. 5fe6cc60680d didn't *add* a
kobject_init_and_add() call; it was there before. And even before
5fe6cc60680d there was no kobject_put() in the error path. Am I
missing something?

For now, I applied this to pci/hotplug for v5.9. I'll update the
commit log to add the Fixes tag if necessary.

> Signed-off-by: Qiushi Wu <[email protected]>
> ---
> drivers/pci/slot.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
> index cc386ef2fa12..3861505741e6 100644
> --- a/drivers/pci/slot.c
> +++ b/drivers/pci/slot.c
> @@ -268,13 +268,16 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
> slot_name = make_slot_name(name);
> if (!slot_name) {
> err = -ENOMEM;
> + kfree(slot);
> goto err;
> }
>
> err = kobject_init_and_add(&slot->kobj, &pci_slot_ktype, NULL,
> "%s", slot_name);
> - if (err)
> + if (err) {
> + kobject_put(&slot->kobj);
> goto err;
> + }
>
> INIT_LIST_HEAD(&slot->list);
> list_add(&slot->list, &parent->slots);
> @@ -293,7 +296,6 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
> mutex_unlock(&pci_slot_mutex);
> return slot;
> err:
> - kfree(slot);
> slot = ERR_PTR(err);
> goto out;
> }
> --
> 2.17.1
>