* [PATCH] usb: core: Fix possible memleak in usb_add_gadget
@ 2021-09-04 15:34 Florian Faber
2021-09-04 16:12 ` Alan Stern
2021-09-05 14:56 ` Greg KH
0 siblings, 2 replies; 6+ messages in thread
From: Florian Faber @ 2021-09-04 15:34 UTC (permalink / raw)
To: gregkh, linux-usb
The memory for the udc structure allocated via kzalloc in line 1295 is
not freed in the error handling code, leading to a memory leak in case
of an error.
Singed-off-by: Florian Faber <faber@faberman.de>
---
drivers/usb/gadget/udc/core.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index 14fdf918ecfe..a1270a44855a 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -1346,6 +1346,8 @@ int usb_add_gadget(struct usb_gadget *gadget)
err_put_udc:
put_device(&udc->dev);
+ kfree(udc);
+ gadget->udc = NULL;
error:
return ret;
--
2.33.0
Flo
--
Machines can do the work, so people have time to think.
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] usb: core: Fix possible memleak in usb_add_gadget
2021-09-04 15:34 [PATCH] usb: core: Fix possible memleak in usb_add_gadget Florian Faber
@ 2021-09-04 16:12 ` Alan Stern
2021-09-05 14:56 ` Greg KH
1 sibling, 0 replies; 6+ messages in thread
From: Alan Stern @ 2021-09-04 16:12 UTC (permalink / raw)
To: Florian Faber; +Cc: gregkh, linux-usb
On Sat, Sep 04, 2021 at 05:34:29PM +0200, Florian Faber wrote:
> The memory for the udc structure allocated via kzalloc in line 1295 is not
> freed in the error handling code, leading to a memory leak in case of an
> error.
>
> Singed-off-by: Florian Faber <faber@faberman.de>
>
> ---
> drivers/usb/gadget/udc/core.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
> index 14fdf918ecfe..a1270a44855a 100644
> --- a/drivers/usb/gadget/udc/core.c
> +++ b/drivers/usb/gadget/udc/core.c
> @@ -1346,6 +1346,8 @@ int usb_add_gadget(struct usb_gadget *gadget)
>
> err_put_udc:
> put_device(&udc->dev);
> + kfree(udc);
> + gadget->udc = NULL;
This is wrong. The udc structure is deallocated by usb_udc_release() (which
is called by put_device()); doing it here too would cause a double-free.
Alan Stern
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] usb: core: Fix possible memleak in usb_add_gadget
2021-09-04 15:34 [PATCH] usb: core: Fix possible memleak in usb_add_gadget Florian Faber
2021-09-04 16:12 ` Alan Stern
@ 2021-09-05 14:56 ` Greg KH
2021-09-05 15:16 ` Florian Faber
1 sibling, 1 reply; 6+ messages in thread
From: Greg KH @ 2021-09-05 14:56 UTC (permalink / raw)
To: Florian Faber; +Cc: linux-usb
On Sat, Sep 04, 2021 at 05:34:29PM +0200, Florian Faber wrote:
> The memory for the udc structure allocated via kzalloc in line 1295 is not
> freed in the error handling code, leading to a memory leak in case of an
> error.
>
> Singed-off-by: Florian Faber <faber@faberman.de>
>
> ---
> drivers/usb/gadget/udc/core.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
> index 14fdf918ecfe..a1270a44855a 100644
> --- a/drivers/usb/gadget/udc/core.c
> +++ b/drivers/usb/gadget/udc/core.c
> @@ -1346,6 +1346,8 @@ int usb_add_gadget(struct usb_gadget *gadget)
>
> err_put_udc:
> put_device(&udc->dev);
> + kfree(udc);
> + gadget->udc = NULL;
>
> error:
> return ret;
> --
> 2.33.0
>
> Flo
> --
> Machines can do the work, so people have time to think.
Did you test this? I think you will find that you just caused a
use-after-free :(
Please read the documentation for device_initialize() for why this is
not the correct thing to do here.
thanks,
greg k-h
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] usb: core: Fix possible memleak in usb_add_gadget
2021-09-05 14:56 ` Greg KH
@ 2021-09-05 15:16 ` Florian Faber
2021-09-05 16:27 ` Greg KH
0 siblings, 1 reply; 6+ messages in thread
From: Florian Faber @ 2021-09-05 15:16 UTC (permalink / raw)
To: Greg KH; +Cc: linux-usb
Greg,
On 9/5/21 4:56 PM, Greg KH wrote:
> On Sat, Sep 04, 2021 at 05:34:29PM +0200, Florian Faber wrote:
>> The memory for the udc structure allocated via kzalloc in line 1295 is not
>> freed in the error handling code, leading to a memory leak in case of an
>> error.
>>
>> Singed-off-by: Florian Faber <faber@faberman.de>
>>
>> ---
>> drivers/usb/gadget/udc/core.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
>> index 14fdf918ecfe..a1270a44855a 100644
>> --- a/drivers/usb/gadget/udc/core.c
>> +++ b/drivers/usb/gadget/udc/core.c
>> @@ -1346,6 +1346,8 @@ int usb_add_gadget(struct usb_gadget *gadget)
>>
>> err_put_udc:
>> put_device(&udc->dev);
>> + kfree(udc);
>> + gadget->udc = NULL;
>>
>> error:
>> return ret;
>> --
>> 2.33.0
>>
>> Flo
>> --
>> Machines can do the work, so people have time to think.
>
> Did you test this? I think you will find that you just caused a
> use-after-free :(
Correct, please forget about this patch.
This 'leak' was found by Klocwork and seemed plausible at first
oversight. Sorry for wasting your time and not checking it further.
> Please read the documentation for device_initialize() for why this is
> not the correct thing to do here.
I know now :) It was a bit counter intuitive that two different methods
are used for memory allocation and freeing.
Regarding the other patch: I found the real culprit in the meantime. The
UDC driver (broadcom iproc udc, out of tree) did not call composite's
disconnect when VBUS is lost. Out of the three gadgets I am using, only
mass storage misbehaved that badly, which led me on the wrong track there.
Flo
--
Machines can do the work, so people have time to think.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] usb: core: Fix possible memleak in usb_add_gadget
2021-09-05 15:16 ` Florian Faber
@ 2021-09-05 16:27 ` Greg KH
2021-09-05 19:58 ` Florian Faber
0 siblings, 1 reply; 6+ messages in thread
From: Greg KH @ 2021-09-05 16:27 UTC (permalink / raw)
To: Florian Faber; +Cc: linux-usb
On Sun, Sep 05, 2021 at 05:16:36PM +0200, Florian Faber wrote:
> Greg,
>
> On 9/5/21 4:56 PM, Greg KH wrote:
> > On Sat, Sep 04, 2021 at 05:34:29PM +0200, Florian Faber wrote:
> > > The memory for the udc structure allocated via kzalloc in line 1295 is not
> > > freed in the error handling code, leading to a memory leak in case of an
> > > error.
> > >
> > > Singed-off-by: Florian Faber <faber@faberman.de>
> > >
> > > ---
> > > drivers/usb/gadget/udc/core.c | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
> > > index 14fdf918ecfe..a1270a44855a 100644
> > > --- a/drivers/usb/gadget/udc/core.c
> > > +++ b/drivers/usb/gadget/udc/core.c
> > > @@ -1346,6 +1346,8 @@ int usb_add_gadget(struct usb_gadget *gadget)
> > >
> > > err_put_udc:
> > > put_device(&udc->dev);
> > > + kfree(udc);
> > > + gadget->udc = NULL;
> > >
> > > error:
> > > return ret;
> > > --
> > > 2.33.0
> > >
> > > Flo
> > > --
> > > Machines can do the work, so people have time to think.
> >
> > Did you test this? I think you will find that you just caused a
> > use-after-free :(
>
> Correct, please forget about this patch.
>
> This 'leak' was found by Klocwork and seemed plausible at first oversight.
> Sorry for wasting your time and not checking it further.
What is "Klockwork"? How can it miss the reference counted logic that
all drivers use in the kernel?
> > Please read the documentation for device_initialize() for why this is
> > not the correct thing to do here.
>
> I know now :) It was a bit counter intuitive that two different methods are
> used for memory allocation and freeing.
The joy of reference counted stuff, sorry.
thanks,
greg k-h
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] usb: core: Fix possible memleak in usb_add_gadget
2021-09-05 16:27 ` Greg KH
@ 2021-09-05 19:58 ` Florian Faber
0 siblings, 0 replies; 6+ messages in thread
From: Florian Faber @ 2021-09-05 19:58 UTC (permalink / raw)
To: Greg KH; +Cc: linux-usb
On 9/5/21 6:27 PM, Greg KH wrote:
> On Sun, Sep 05, 2021 at 05:16:36PM +0200, Florian Faber wrote:
>> This 'leak' was found by Klocwork and seemed plausible at first oversight.
>> Sorry for wasting your time and not checking it further.
>
> What is "Klockwork"?
Some static code analysis tool. I did not know it either.
> How can it miss the reference counted logic that
> all drivers use in the kernel?
Obviously it is not running like clockwork :)
Anyway, got the problem fixed, sorry for the noise.
Flo
--
Machines can do the work, so people have time to think.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-09-05 20:04 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2021-09-04 15:34 [PATCH] usb: core: Fix possible memleak in usb_add_gadget Florian Faber
2021-09-04 16:12 ` Alan Stern
2021-09-05 14:56 ` Greg KH
2021-09-05 15:16 ` Florian Faber
2021-09-05 16:27 ` Greg KH
2021-09-05 19:58 ` Florian Faber
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