if device_register() returned an error! Always use put_device()
to give up the reference initialized.
Arvind Yadav (2):
[PATCH 1/2] mtd: use put_device() if device_register fail
[PATCH 2/2] mtd: ubi: use put_device() if device_register fail
drivers/mtd/mtdcore.c | 1 +
drivers/mtd/ubi/vmt.c | 1 +
2 files changed, 2 insertions(+)
--
1.9.1
if device_register() returned an error! Always use put_device()
to give up the reference initialized.
Signed-off-by: Arvind Yadav <[email protected]>
---
drivers/mtd/mtdcore.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 28553c8..4d77ca2 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -586,6 +586,7 @@ int add_mtd_device(struct mtd_info *mtd)
return 0;
fail_added:
+ put_device(&mtd->dev);
of_node_put(mtd_get_of_node(mtd));
idr_remove(&mtd_idr, i);
fail_locked:
--
1.9.1
if device_register() returned an error! Always use put_device()
to give up the reference initialized.
Signed-off-by: Arvind Yadav <[email protected]>
---
drivers/mtd/ubi/vmt.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index 3fd8d7f..db85b68 100644
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -609,6 +609,7 @@ int ubi_add_volume(struct ubi_device *ubi, struct ubi_volume *vol)
return err;
out_cdev:
+ put_device(&vol->dev);
cdev_del(&vol->cdev);
return err;
}
--
1.9.1
Am Freitag, 9. M?rz 2018, 11:50:47 CET schrieb Arvind Yadav:
> if device_register() returned an error! Always use put_device()
> to give up the reference initialized.
>
> Arvind Yadav (2):
> [PATCH 1/2] mtd: use put_device() if device_register fail
> [PATCH 2/2] mtd: ubi: use put_device() if device_register fail
Uhh, this is not obvious. Does device_register() really always return with a
reference held in all (error) cases?
Thanks,
//richard
On Monday 12 March 2018 01:05 AM, Richard Weinberger wrote:
> Am Freitag, 9. M?rz 2018, 11:50:47 CET schrieb Arvind Yadav:
>> if device_register() returned an error! Always use put_device()
>> to give up the reference initialized.
>>
>> Arvind Yadav (2):
>> [PATCH 1/2] mtd: use put_device() if device_register fail
>> [PATCH 2/2] mtd: ubi: use put_device() if device_register fail
> Uhh, this is not obvious. Does device_register() really always return with a
> reference held in all (error) cases?
>
> Thanks,
> //richard
if device_register() returned an error! Always use put_device()
to give up the reference initialized.(-- Please see the comment
for device_register() ). put_device() is able to handle those case
where it'll not return a reference.
~arvind
Arvind,
Am Montag, 12. M?rz 2018, 06:51:24 CET schrieb Arvind Yadav:
> On Monday 12 March 2018 01:05 AM, Richard Weinberger wrote:
> > Am Freitag, 9. M?rz 2018, 11:50:47 CET schrieb Arvind Yadav:
> >> if device_register() returned an error! Always use put_device()
> >> to give up the reference initialized.
> >>
> >> Arvind Yadav (2):
> >> [PATCH 1/2] mtd: use put_device() if device_register fail
> >> [PATCH 2/2] mtd: ubi: use put_device() if device_register fail
> >
> > Uhh, this is not obvious. Does device_register() really always return with
> > a reference held in all (error) cases?
> >
> > Thanks,
> > //richard
>
> if device_register() returned an error! Always use put_device()
> to give up the reference initialized.(-- Please see the comment
> for device_register() ). put_device() is able to handle those case
> where it'll not return a reference.
You are right.
For both patches:
Acked-by: Richard Weinberger <[email protected]>
Thanks,
//richard
On Fri, 9 Mar 2018 16:20:48 +0530
Arvind Yadav <[email protected]> wrote:
> if device_register() returned an error! Always use put_device()
> to give up the reference initialized.
>
> Signed-off-by: Arvind Yadav <[email protected]>
> ---
> drivers/mtd/mtdcore.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index 28553c8..4d77ca2 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -586,6 +586,7 @@ int add_mtd_device(struct mtd_info *mtd)
> return 0;
>
> fail_added:
> + put_device(&mtd->dev);
Not sure this is a good idea: the put_device() call will trigger
an mtd_devtype->release(), which will in turn call device_destroy() on
something that does not exist yet. Not sure if this is a real problem,
but it does not look like the right thing to do.
> of_node_put(mtd_get_of_node(mtd));
You're referencing an object that is supposed to have been
freed/released by the put_device() call. Again, it's not really a
problem because in our case ->release() does not free the mtd object
(as is usually done in other parts of the kernel), but it still looks
wrong. It's probably better to move the of_node_put() and the below
idr_remove() call in the ->release() hook if you want to use
put_device().
> idr_remove(&mtd_idr, i);
> fail_locked:
--
Boris Brezillon, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com
On Fri, 9 Mar 2018 16:20:49 +0530
Arvind Yadav <[email protected]> wrote:
> if device_register() returned an error! Always use put_device()
> to give up the reference initialized.
>
> Signed-off-by: Arvind Yadav <[email protected]>
> ---
> drivers/mtd/ubi/vmt.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
> index 3fd8d7f..db85b68 100644
> --- a/drivers/mtd/ubi/vmt.c
> +++ b/drivers/mtd/ubi/vmt.c
> @@ -609,6 +609,7 @@ int ubi_add_volume(struct ubi_device *ubi, struct ubi_volume *vol)
> return err;
>
> out_cdev:
> + put_device(&vol->dev);
> cdev_del(&vol->cdev);
use-after-free bug here: put_device() has freed the vol obj, and you're
dereferencing the pointer just after that.
> return err;
> }
--
Boris Brezillon, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com
Am Mittwoch, 14. M?rz 2018, 19:56:52 CET schrieb Boris Brezillon:
> On Fri, 9 Mar 2018 16:20:49 +0530
>
> Arvind Yadav <[email protected]> wrote:
> > if device_register() returned an error! Always use put_device()
> > to give up the reference initialized.
> >
> > Signed-off-by: Arvind Yadav <[email protected]>
> > ---
> >
> > drivers/mtd/ubi/vmt.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
> > index 3fd8d7f..db85b68 100644
> > --- a/drivers/mtd/ubi/vmt.c
> > +++ b/drivers/mtd/ubi/vmt.c
> > @@ -609,6 +609,7 @@ int ubi_add_volume(struct ubi_device *ubi, struct
> > ubi_volume *vol)>
> > return err;
> >
> > out_cdev:
> > + put_device(&vol->dev);
> >
> > cdev_del(&vol->cdev);
>
> use-after-free bug here: put_device() has freed the vol obj, and you're
> dereferencing the pointer just after that.
eeek, thanks for looking at more context.
Arvind, while you are right that put_device() is missing, please double check
that freeing the devices is also correct.
Thanks,
//richard
On Thursday 15 March 2018 12:55 AM, Richard Weinberger wrote:
> Am Mittwoch, 14. M?rz 2018, 19:56:52 CET schrieb Boris Brezillon:
>> On Fri, 9 Mar 2018 16:20:49 +0530
>>
>> Arvind Yadav <[email protected]> wrote:
>>> if device_register() returned an error! Always use put_device()
>>> to give up the reference initialized.
>>>
>>> Signed-off-by: Arvind Yadav <[email protected]>
>>> ---
>>>
>>> drivers/mtd/ubi/vmt.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
>>> index 3fd8d7f..db85b68 100644
>>> --- a/drivers/mtd/ubi/vmt.c
>>> +++ b/drivers/mtd/ubi/vmt.c
>>> @@ -609,6 +609,7 @@ int ubi_add_volume(struct ubi_device *ubi, struct
>>> ubi_volume *vol)>
>>> return err;
>>>
>>> out_cdev:
>>> + put_device(&vol->dev);
>>>
>>> cdev_del(&vol->cdev);
>> use-after-free bug here: put_device() has freed the vol obj, and you're
>> dereferencing the pointer just after that.
Thanks Boris, to point out this error.
> eeek, thanks for looking at more context.
> Arvind, while you are right that put_device() is missing, please double check
> that freeing the devices is also correct.
>
> Thanks,
> //richard
Sorry for that. I will take care of this.
~arvind
On Wednesday 14 March 2018 08:06 PM, Boris Brezillon wrote:
> On Fri, 9 Mar 2018 16:20:48 +0530
> Arvind Yadav <[email protected]> wrote:
>
>> if device_register() returned an error! Always use put_device()
>> to give up the reference initialized.
>>
>> Signed-off-by: Arvind Yadav <[email protected]>
>> ---
>> drivers/mtd/mtdcore.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
>> index 28553c8..4d77ca2 100644
>> --- a/drivers/mtd/mtdcore.c
>> +++ b/drivers/mtd/mtdcore.c
>> @@ -586,6 +586,7 @@ int add_mtd_device(struct mtd_info *mtd)
>> return 0;
>>
>> fail_added:
>> + put_device(&mtd->dev);
> Not sure this is a good idea: the put_device() call will trigger
> an mtd_devtype->release(), which will in turn call device_destroy() on
> something that does not exist yet. Not sure if this is a real problem,
> but it does not look like the right thing to do.
>
yes, you are correct. No need to call put_device().
which can cause other problem.
>> of_node_put(mtd_get_of_node(mtd));
> You're referencing an object that is supposed to have been
> freed/released by the put_device() call. Again, it's not really a
> problem because in our case ->release() does not free the mtd object
> (as is usually done in other parts of the kernel), but it still looks
> wrong. It's probably better to move the of_node_put() and the below
> idr_remove() call in the ->release() hook if you want to use
> put_device().
>
>> idr_remove(&mtd_idr, i);
Sure, we can move put_device() below this. But need to check
how we can add hook in release.
>
>> fail_locked:
>
>
~arvind