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SubjectRe: [PATCH v2] usb: storage: add error handling for kcalloc
On Mon, 25 Jun 2018, Greg Kroah-Hartman wrote:

> On Thu, Jun 14, 2018 at 09:29:11PM +0800, Zhouyang Jia wrote:
> > When kcalloc fails, the lack of error-handling code may
> > cause unexpected results.
> >
> > This patch adds error-handling code after calling kcalloc.
> >
> > Signed-off-by: Zhouyang Jia <jiazhouyang09@gmail.com>
> > Acked-by: Alan Stern <stern@rowland.harvard.edu>
> > ---
> > v1->v2:
> > - Remove pr_warn statement.
> > ---
> > drivers/usb/storage/alauda.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/usb/storage/alauda.c b/drivers/usb/storage/alauda.c
> > index 900591d..4e17609 100644
> > --- a/drivers/usb/storage/alauda.c
> > +++ b/drivers/usb/storage/alauda.c
> > @@ -437,6 +437,9 @@ static int alauda_init_media(struct us_data *us)
> > + MEDIA_INFO(us).blockshift + MEDIA_INFO(us).pageshift);
> > MEDIA_INFO(us).pba_to_lba = kcalloc(num_zones, sizeof(u16*), GFP_NOIO);
> > MEDIA_INFO(us).lba_to_pba = kcalloc(num_zones, sizeof(u16*), GFP_NOIO);
> > + if ((MEDIA_INFO(us).pba_to_lba == NULL)
> > + || (MEDIA_INFO(us).lba_to_pba == NULL))
> > + return USB_STOR_TRANSPORT_ERROR;
>
> You just leaked memory if only one of these succeeded :(

That's not really true. The memory gets deallocated later on in any
case, when alauda_info_destructor() calls alauda_free_maps() if not
before.

More troubling is the fact that this routine (i.e, alauda_init_media)
gets called from only one place, in alauda_check_media, and the caller
completely ignores the return value! Furthermore, the caller always
returns USB_STOR_TRANSPORT_FAILED.

So on the whole, I don't think this patch is going to make any
difference to the driver's operation.

Alan Stern

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