[PATCH] Bluetooth: hci_core: Use ERR_PTR instead of NULL

[PATCH] Bluetooth: hci_core: Use ERR_PTR instead of NULL

[Khalid Masum]

Failure of kzalloc to allocate memory is not reported. Return Error
pointer to ENOMEM if memory allocation fails. This will increase
readability and will make the function easier to use in future.

Signed-off-by: Khalid Masum <khalid.masum.92@gmail.com>
---
 drivers/bluetooth/btusb.c | 4 ++--
 net/bluetooth/hci_core.c  | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index e25fcd49db70..3407762b3b15 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -3692,8 +3692,8 @@ static int btusb_probe(struct usb_interface *intf,
 	data->recv_acl = hci_recv_frame;
 
 	hdev = hci_alloc_dev_priv(priv_size);
-	if (!hdev)
-		return -ENOMEM;
+	if (IS_ERR(hdev))
+		return PTR_ERR(hdev);
 
 	hdev->bus = HCI_USB;
 	hci_set_drvdata(hdev, data);
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index a0f99baafd35..ea50767e02bf 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -2419,7 +2419,7 @@ struct hci_dev *hci_alloc_dev_priv(int sizeof_priv)
 
 	hdev = kzalloc(alloc_size, GFP_KERNEL);
 	if (!hdev)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	hdev->pkt_type  = (HCI_DM1 | HCI_DH1 | HCI_HV1);
 	hdev->esco_type = (ESCO_HV1);
-- 
2.36.1

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Re: [PATCH] Bluetooth: hci_core: Use ERR_PTR instead of NULL

[Pavel Skripkin]

Hi Khalid,

Khalid Masum <khalid.masum.92@gmail.com> says:
> Failure of kzalloc to allocate memory is not reported. Return Error
> pointer to ENOMEM if memory allocation fails. This will increase
> readability and will make the function easier to use in future.
> 
> Signed-off-by: Khalid Masum <khalid.masum.92@gmail.com>
> ---

[snip]

> index a0f99baafd35..ea50767e02bf 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -2419,7 +2419,7 @@ struct hci_dev *hci_alloc_dev_priv(int sizeof_priv)
>   
>   	hdev = kzalloc(alloc_size, GFP_KERNEL);
>   	if (!hdev)
> -		return NULL;
> +		return ERR_PTR(-ENOMEM);
>   

This will break all callers of hci_alloc_dev(). All callers expect NULL 
in case of an error, so you will leave them with wrong pointer.

Also, allocation functionS return an error only in case of ENOMEM, so 
initial code is fine, IMO




Thanks,
--Pavel Skripkin
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Re: [PATCH] Bluetooth: hci_core: Use ERR_PTR instead of NULL

[Khalid Masum]

On Sun, Jul 17, 2022 at 10:17 PM Pavel Skripkin <paskripkin@gmail.com> wrote:
>
> Hi Khalid,
>
> Khalid Masum <khalid.masum.92@gmail.com> says:
> > Failure of kzalloc to allocate memory is not reported. Return Error
> > pointer to ENOMEM if memory allocation fails. This will increase
> > readability and will make the function easier to use in future.
> >
> > Signed-off-by: Khalid Masum <khalid.masum.92@gmail.com>
> > ---
>
> [snip]
>
> > index a0f99baafd35..ea50767e02bf 100644
> > --- a/net/bluetooth/hci_core.c
> > +++ b/net/bluetooth/hci_core.c
> > @@ -2419,7 +2419,7 @@ struct hci_dev *hci_alloc_dev_priv(int sizeof_priv)
> >
> >       hdev = kzalloc(alloc_size, GFP_KERNEL);
> >       if (!hdev)
> > -             return NULL;
> > +             return ERR_PTR(-ENOMEM);
> >
>
> This will break all callers of hci_alloc_dev(). All callers expect NULL
> in case of an error, so you will leave them with wrong pointer.

You are right. All callers of hci_alloc_dev() need to be able to handle
the error pointer. I shall send a V2 with all the callers of hci_alloc_dev
handling the ERR_PTR.

> Also, allocation functionS return an error only in case of ENOMEM, so
> initial code is fine, IMO
>

I think it makes the memory allocation error handling look to be a bit
different from what we usually do while allocating memory which is,
returning an error or an error pointer. Here we are returning a NULL
without any context, making it a bit unreadable. So I think returning
an error pointer is better. If I am not mistaken, this also complies with
the return convention:
https://www.kernel.org/doc/htmldocs/kernel-hacking/convention-returns.html

>
> Thanks,
> --Pavel Skripkin


Thanks,
  -- Khalid Masum
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Re: [PATCH] Bluetooth: hci_core: Use ERR_PTR instead of NULL

[Luiz Augusto von Dentz]

Hi Khalid,

On Sun, Jul 17, 2022 at 11:34 AM Khalid Masum <khalid.masum.92@gmail.com> wrote:
>
> On Sun, Jul 17, 2022 at 10:17 PM Pavel Skripkin <paskripkin@gmail.com> wrote:
> >
> > Hi Khalid,
> >
> > Khalid Masum <khalid.masum.92@gmail.com> says:
> > > Failure of kzalloc to allocate memory is not reported. Return Error
> > > pointer to ENOMEM if memory allocation fails. This will increase
> > > readability and will make the function easier to use in future.
> > >
> > > Signed-off-by: Khalid Masum <khalid.masum.92@gmail.com>
> > > ---
> >
> > [snip]
> >
> > > index a0f99baafd35..ea50767e02bf 100644
> > > --- a/net/bluetooth/hci_core.c
> > > +++ b/net/bluetooth/hci_core.c
> > > @@ -2419,7 +2419,7 @@ struct hci_dev *hci_alloc_dev_priv(int sizeof_priv)
> > >
> > >       hdev = kzalloc(alloc_size, GFP_KERNEL);
> > >       if (!hdev)
> > > -             return NULL;
> > > +             return ERR_PTR(-ENOMEM);
> > >
> >
> > This will break all callers of hci_alloc_dev(). All callers expect NULL
> > in case of an error, so you will leave them with wrong pointer.
>
> You are right. All callers of hci_alloc_dev() need to be able to handle
> the error pointer. I shall send a V2 with all the callers of hci_alloc_dev
> handling the ERR_PTR.
>
> > Also, allocation functionS return an error only in case of ENOMEM, so
> > initial code is fine, IMO
> >

If there just a single error like ENOMEM then Id say this is fine,
just as it is fine for kzalloc.

> I think it makes the memory allocation error handling look to be a bit
> different from what we usually do while allocating memory which is,
> returning an error or an error pointer. Here we are returning a NULL
> without any context, making it a bit unreadable. So I think returning
> an error pointer is better. If I am not mistaken, this also complies with
> the return convention:
> https://www.kernel.org/doc/htmldocs/kernel-hacking/convention-returns.html

Not sure if that would apply to code that is basically a wrapper of kzalloc.

> >
> > Thanks,
> > --Pavel Skripkin
>
>
> Thanks,
>   -- Khalid Masum



-- 
Luiz Augusto von Dentz
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Re: [PATCH] Bluetooth: hci_core: Use ERR_PTR instead of NULL

[Khalid Masum]

On Tue, Jul 19, 2022 at 5:04 AM Luiz Augusto von Dentz
<luiz.dentz@gmail.com> wrote:
>
> Hi Khalid,
>
> On Sun, Jul 17, 2022 at 11:34 AM Khalid Masum <khalid.masum.92@gmail.com> wrote:
> >
> > On Sun, Jul 17, 2022 at 10:17 PM Pavel Skripkin <paskripkin@gmail.com> wrote:
> > >
> > > Hi Khalid,
> > >
> > > Khalid Masum <khalid.masum.92@gmail.com> says:
> > > > Failure of kzalloc to allocate memory is not reported. Return Error
> > > > pointer to ENOMEM if memory allocation fails. This will increase
> > > > readability and will make the function easier to use in future.
> > > >
> > > > Signed-off-by: Khalid Masum <khalid.masum.92@gmail.com>
> > > > ---
> > >
> > > [snip]
> > >
> > > > index a0f99baafd35..ea50767e02bf 100644
> > > > --- a/net/bluetooth/hci_core.c
> > > > +++ b/net/bluetooth/hci_core.c
> > > > @@ -2419,7 +2419,7 @@ struct hci_dev *hci_alloc_dev_priv(int sizeof_priv)
> > > >
> > > >       hdev = kzalloc(alloc_size, GFP_KERNEL);
> > > >       if (!hdev)
> > > > -             return NULL;
> > > > +             return ERR_PTR(-ENOMEM);
> > > >
> > >
> > > This will break all callers of hci_alloc_dev(). All callers expect NULL
> > > in case of an error, so you will leave them with wrong pointer.
> >
> > You are right. All callers of hci_alloc_dev() need to be able to handle
> > the error pointer. I shall send a V2 with all the callers of hci_alloc_dev
> > handling the ERR_PTR.
> >
> > > Also, allocation functionS return an error only in case of ENOMEM, so
> > > initial code is fine, IMO
> > >
>
> If there just a single error like ENOMEM then Id say this is fine,
> just as it is fine for kzalloc.
>
> > I think it makes the memory allocation error handling look to be a bit
> > different from what we usually do while allocating memory which is,
> > returning an error or an error pointer. Here we are returning a NULL
> > without any context, making it a bit unreadable. So I think returning
> > an error pointer is better. If I am not mistaken, this also complies with
> > the return convention:
> > https://www.kernel.org/doc/htmldocs/kernel-hacking/convention-returns.html
>
> Not sure if that would apply to code that is basically a wrapper of kzalloc.

I got you.
> > > Thanks,
> > > --Pavel Skripkin
> >
> >
> > Thanks,
> >   -- Khalid Masum
>
>
>
> --
> Luiz Augusto von Dentz

Thanks,
  -- Khalid Masum
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