Re: [PATCH] net: dsa: loop: Check for memory allocation failure

[Joe Perches]

On Mon, 2017-05-08 at 17:35 -0700, Florian Fainelli wrote:
> On 05/08/2017 04:46 PM, Julia Lawall wrote:
> > On Mon, 8 May 2017, Joe Perches wrote:
> > > Each time -EPROBE_DEFER occurs, another set of calls to
> > > dsa_switch_alloc and dev_kzalloc also occurs.
> > > 
> > > Perhaps it'd be better to do:
> > > 
> > >   if (ps->netdev) {
> > >   devm_kfree(>dev, ps);
> > >   devm_kfree(>dev, ds);
> > >   return -EPROBE_DEFER;
> > >   }
> > 
> > Is EPROBE_DEFER handled differently than other kinds of errors?
> 
> In the core device driver model, yes, EPROBE_DEFER is treated
> differently than other errors because it puts the driver on a retry queue.
> 
> EPROBE_DEFER is already a slow and exceptional path, and this is a
> mock-up driver, so I am not sure what value there is in trying to
> balance devm_kzalloc() with corresponding devm_kfree()...

Example code should be as correct as possible.

Re: [PATCH] net: dsa: loop: Check for memory allocation failure

[Julia Lawall]

On Mon, 8 May 2017, Florian Fainelli wrote:

> On 05/08/2017 04:46 PM, Julia Lawall wrote:
> >
> >
> > On Mon, 8 May 2017, Joe Perches wrote:
> >
> >> On Mon, 2017-05-08 at 20:32 +0800, Julia Lawall wrote:
> >>>
> >>> On Mon, 8 May 2017, David Laight wrote:
> >>>
>  From: Christophe JAILLET
> > Sent: 06 May 2017 06:30
> > If 'devm_kzalloc' fails, a NULL pointer will be dereferenced.
> > Return -ENOMEM instead, as done for some other memory allocation just a
> > few lines above.
> 
>  ...
> > --- a/drivers/net/dsa/dsa_loop.c
> > +++ b/drivers/net/dsa/dsa_loop.c
> > @@ -256,6 +256,9 @@ static int dsa_loop_drv_probe(struct mdio_device 
> > *mdiodev)
> > return -ENOMEM;
> >
> > ps = devm_kzalloc(>dev, sizeof(*ps), GFP_KERNEL);
> > +   if (!ps)
> > +   return -ENOMEM;
> > +
> > ps->netdev = dev_get_by_name(_net, pdata->netdev);
> > if (!ps->netdev)
> > return -EPROBE_DEFER;
> 
>  On the face if it this code leaks like a sieve.
> >>>
> >>> I don't think so.  The allocations (dsa_switch_alloc and devm_kzalloc) use
> >>> devm functions.
> >>
> >> It's at least wasteful.
> >>
> >> Each time -EPROBE_DEFER occurs, another set of calls to
> >> dsa_switch_alloc and dev_kzalloc also occurs.
> >>
> >> Perhaps it'd be better to do:
> >>
> >>if (ps->netdev) {
> >>devm_kfree(>dev, ps);
> >>devm_kfree(>dev, ds);
> >>return -EPROBE_DEFER;
> >>}
> >
> > Is EPROBE_DEFER handled differently than other kinds of errors?
>
> In the core device driver model, yes, EPROBE_DEFER is treated
> differently than other errors because it puts the driver on a retry queue.
>
> EPROBE_DEFER is already a slow and exceptional path, and this is a
> mock-up driver, so I am not sure what value there is in trying to
> balance devm_kzalloc() with corresponding devm_kfree()...

OK, thanks for the explanation.

julia

Re: [PATCH] net: dsa: loop: Check for memory allocation failure

[Florian Fainelli]

On 05/08/2017 04:46 PM, Julia Lawall wrote:
> 
> 
> On Mon, 8 May 2017, Joe Perches wrote:
> 
>> On Mon, 2017-05-08 at 20:32 +0800, Julia Lawall wrote:
>>>
>>> On Mon, 8 May 2017, David Laight wrote:
>>>
 From: Christophe JAILLET
> Sent: 06 May 2017 06:30
> If 'devm_kzalloc' fails, a NULL pointer will be dereferenced.
> Return -ENOMEM instead, as done for some other memory allocation just a
> few lines above.

 ...
> --- a/drivers/net/dsa/dsa_loop.c
> +++ b/drivers/net/dsa/dsa_loop.c
> @@ -256,6 +256,9 @@ static int dsa_loop_drv_probe(struct mdio_device 
> *mdiodev)
>   return -ENOMEM;
>
>   ps = devm_kzalloc(>dev, sizeof(*ps), GFP_KERNEL);
> + if (!ps)
> + return -ENOMEM;
> +
>   ps->netdev = dev_get_by_name(_net, pdata->netdev);
>   if (!ps->netdev)
>   return -EPROBE_DEFER;

 On the face if it this code leaks like a sieve.
>>>
>>> I don't think so.  The allocations (dsa_switch_alloc and devm_kzalloc) use
>>> devm functions.
>>
>> It's at least wasteful.
>>
>> Each time -EPROBE_DEFER occurs, another set of calls to
>> dsa_switch_alloc and dev_kzalloc also occurs.
>>
>> Perhaps it'd be better to do:
>>
>>  if (ps->netdev) {
>>  devm_kfree(>dev, ps);
>>  devm_kfree(>dev, ds);
>>  return -EPROBE_DEFER;
>>  }
> 
> Is EPROBE_DEFER handled differently than other kinds of errors?

In the core device driver model, yes, EPROBE_DEFER is treated
differently than other errors because it puts the driver on a retry queue.

EPROBE_DEFER is already a slow and exceptional path, and this is a
mock-up driver, so I am not sure what value there is in trying to
balance devm_kzalloc() with corresponding devm_kfree()...
-- 
Florian

Re: [PATCH] net: dsa: loop: Check for memory allocation failure

[Julia Lawall]

On Mon, 8 May 2017, Joe Perches wrote:

> On Mon, 2017-05-08 at 20:32 +0800, Julia Lawall wrote:
> >
> > On Mon, 8 May 2017, David Laight wrote:
> >
> > > From: Christophe JAILLET
> > > > Sent: 06 May 2017 06:30
> > > > If 'devm_kzalloc' fails, a NULL pointer will be dereferenced.
> > > > Return -ENOMEM instead, as done for some other memory allocation just a
> > > > few lines above.
> > >
> > > ...
> > > > --- a/drivers/net/dsa/dsa_loop.c
> > > > +++ b/drivers/net/dsa/dsa_loop.c
> > > > @@ -256,6 +256,9 @@ static int dsa_loop_drv_probe(struct mdio_device 
> > > > *mdiodev)
> > > > return -ENOMEM;
> > > >
> > > > ps = devm_kzalloc(>dev, sizeof(*ps), GFP_KERNEL);
> > > > +   if (!ps)
> > > > +   return -ENOMEM;
> > > > +
> > > > ps->netdev = dev_get_by_name(_net, pdata->netdev);
> > > > if (!ps->netdev)
> > > > return -EPROBE_DEFER;
> > >
> > > On the face if it this code leaks like a sieve.
> >
> > I don't think so.  The allocations (dsa_switch_alloc and devm_kzalloc) use
> > devm functions.
>
> It's at least wasteful.
>
> Each time -EPROBE_DEFER occurs, another set of calls to
> dsa_switch_alloc and dev_kzalloc also occurs.
>
> Perhaps it'd be better to do:
>
>   if (ps->netdev) {
>   devm_kfree(>dev, ps);
>   devm_kfree(>dev, ds);
>   return -EPROBE_DEFER;
>   }

Is EPROBE_DEFER handled differently than other kinds of errors?

julia


>
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Re: [PATCH] net: dsa: loop: Check for memory allocation failure

[Joe Perches]

On Mon, 2017-05-08 at 20:32 +0800, Julia Lawall wrote:
> 
> On Mon, 8 May 2017, David Laight wrote:
> 
> > From: Christophe JAILLET
> > > Sent: 06 May 2017 06:30
> > > If 'devm_kzalloc' fails, a NULL pointer will be dereferenced.
> > > Return -ENOMEM instead, as done for some other memory allocation just a
> > > few lines above.
> > 
> > ...
> > > --- a/drivers/net/dsa/dsa_loop.c
> > > +++ b/drivers/net/dsa/dsa_loop.c
> > > @@ -256,6 +256,9 @@ static int dsa_loop_drv_probe(struct mdio_device 
> > > *mdiodev)
> > >   return -ENOMEM;
> > > 
> > >   ps = devm_kzalloc(>dev, sizeof(*ps), GFP_KERNEL);
> > > + if (!ps)
> > > + return -ENOMEM;
> > > +
> > >   ps->netdev = dev_get_by_name(_net, pdata->netdev);
> > >   if (!ps->netdev)
> > >   return -EPROBE_DEFER;
> > 
> > On the face if it this code leaks like a sieve.
> 
> I don't think so.  The allocations (dsa_switch_alloc and devm_kzalloc) use
> devm functions.

It's at least wasteful.

Each time -EPROBE_DEFER occurs, another set of calls to
dsa_switch_alloc and dev_kzalloc also occurs.

Perhaps it'd be better to do:

if (ps->netdev) {
devm_kfree(>dev, ps);
devm_kfree(>dev, ds);
return -EPROBE_DEFER;
}

Re: [PATCH] net: dsa: loop: Check for memory allocation failure

[David Miller]

From: Christophe JAILLET 
Date: Sat,  6 May 2017 07:29:45 +0200

> If 'devm_kzalloc' fails, a NULL pointer will be dereferenced.
> Return -ENOMEM instead, as done for some other memory allocation just a
> few lines above.
> 
> Fixes: 98cd1552ea27 ("net: dsa: Mock-up driver")
> 
> Signed-off-by: Christophe JAILLET 

Please do not separate "Fixes: " tags from signoffs and acks with
empty lines in the future, thank you.

Applied and queued up for -stable.

RE: [PATCH] net: dsa: loop: Check for memory allocation failure

[Julia Lawall]

On Mon, 8 May 2017, David Laight wrote:

> From: Christophe JAILLET
> > Sent: 06 May 2017 06:30
> > If 'devm_kzalloc' fails, a NULL pointer will be dereferenced.
> > Return -ENOMEM instead, as done for some other memory allocation just a
> > few lines above.
> ...
> > --- a/drivers/net/dsa/dsa_loop.c
> > +++ b/drivers/net/dsa/dsa_loop.c
> > @@ -256,6 +256,9 @@ static int dsa_loop_drv_probe(struct mdio_device 
> > *mdiodev)
> > return -ENOMEM;
> >
> > ps = devm_kzalloc(>dev, sizeof(*ps), GFP_KERNEL);
> > +   if (!ps)
> > +   return -ENOMEM;
> > +
> > ps->netdev = dev_get_by_name(_net, pdata->netdev);
> > if (!ps->netdev)
> > return -EPROBE_DEFER;
>
> On the face if it this code leaks like a sieve.

I don't think so.  The allocations (dsa_switch_alloc and devm_kzalloc) use
devm functions.

julia

RE: [PATCH] net: dsa: loop: Check for memory allocation failure

[David Laight]

From: Christophe JAILLET
> Sent: 06 May 2017 06:30
> If 'devm_kzalloc' fails, a NULL pointer will be dereferenced.
> Return -ENOMEM instead, as done for some other memory allocation just a
> few lines above.
...
> --- a/drivers/net/dsa/dsa_loop.c
> +++ b/drivers/net/dsa/dsa_loop.c
> @@ -256,6 +256,9 @@ static int dsa_loop_drv_probe(struct mdio_device *mdiodev)
>   return -ENOMEM;
> 
>   ps = devm_kzalloc(>dev, sizeof(*ps), GFP_KERNEL);
> + if (!ps)
> + return -ENOMEM;
> +
>   ps->netdev = dev_get_by_name(_net, pdata->netdev);
>   if (!ps->netdev)
>   return -EPROBE_DEFER;

On the face if it this code leaks like a sieve.

David

Re: [PATCH] net: dsa: loop: Check for memory allocation failure

[Florian Fainelli]

Le 05/05/17 à 22:29, Christophe JAILLET a écrit :
> If 'devm_kzalloc' fails, a NULL pointer will be dereferenced.
> Return -ENOMEM instead, as done for some other memory allocation just a
> few lines above.
> 
> Fixes: 98cd1552ea27 ("net: dsa: Mock-up driver")
> 
> Signed-off-by: Christophe JAILLET 

Acked-by: Florian Fainelli 
-- 
Florian

Re: [PATCH] net: dsa: loop: Check for memory allocation failure

[Andrew Lunn]

On Sat, May 06, 2017 at 07:29:45AM +0200, Christophe JAILLET wrote:
> If 'devm_kzalloc' fails, a NULL pointer will be dereferenced.
> Return -ENOMEM instead, as done for some other memory allocation just a
> few lines above.
> 
> Fixes: 98cd1552ea27 ("net: dsa: Mock-up driver")
> 
> Signed-off-by: Christophe JAILLET 

Reviewed-by: Andrew Lunn 

Andrew

[PATCH] net: dsa: loop: Check for memory allocation failure

[Christophe JAILLET]

If 'devm_kzalloc' fails, a NULL pointer will be dereferenced.
Return -ENOMEM instead, as done for some other memory allocation just a
few lines above.

Fixes: 98cd1552ea27 ("net: dsa: Mock-up driver")

Signed-off-by: Christophe JAILLET 
---
 drivers/net/dsa/dsa_loop.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/dsa/dsa_loop.c b/drivers/net/dsa/dsa_loop.c
index f0fc4de4fc9a..a19e1781e9bb 100644
--- a/drivers/net/dsa/dsa_loop.c
+++ b/drivers/net/dsa/dsa_loop.c
@@ -256,6 +256,9 @@ static int dsa_loop_drv_probe(struct mdio_device *mdiodev)
return -ENOMEM;
 
ps = devm_kzalloc(>dev, sizeof(*ps), GFP_KERNEL);
+   if (!ps)
+   return -ENOMEM;
+
ps->netdev = dev_get_by_name(_net, pdata->netdev);
if (!ps->netdev)
return -EPROBE_DEFER;
-- 
2.11.0