Re: [PATCH] misc: ocxl: fix possible double free in ocxl_file_register_afu

[Hangyu Hua]

On 2022/4/19 17:09, Frederic Barrat wrote:
> On 18/04/2022 10:57, Hangyu Hua wrote:
> > info_release() will be called in device_unregister() when info->dev's
> > reference count is 0. So there is no need to call ocxl_afu_put() and
> > kfree() again.
> >
> > Fix this by adding free_minor() and return to err_unregister error path.
> >
> > Fixes: 75ca758adbaf ("ocxl: Create a clear delineation between ocxl 
> > backend & frontend")
> > Signed-off-by: Hangyu Hua <hbh25y@xxxxxxxxx>
> > ---
>
>
> Thanks for fixing that error path!
> I'm now thinking it would be cleaner to have the call to free_minor() in 
> the info_release() callback but that would be another patch.
> In any case:
> Acked-by: Frederic Barrat <fbarrat@xxxxxxxxxxxxx>
>
>    Fred

I think it is a good idea to use callbacks to handle all garbage 
collections. And free_minor is used only in ocxl_file_register_afu() 
andocxl_file_unregister_afu(). So this should only require minor changes.

Thanks.

> >   drivers/misc/ocxl/file.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/misc/ocxl/file.c b/drivers/misc/ocxl/file.c
> > index d881f5e40ad9..6777c419a8da 100644
> > --- a/drivers/misc/ocxl/file.c
> > +++ b/drivers/misc/ocxl/file.c
> > @@ -556,7 +556,9 @@ int ocxl_file_register_afu(struct ocxl_afu *afu)
> >   err_unregister:
> >       ocxl_sysfs_unregister_afu(info); // safe to call even if 
> > register failed
> > +    free_minor(info);
> >       device_unregister(&info->dev);
> > +    return rc;
> >   err_put:
> >       ocxl_afu_put(afu);
> >       free_minor(info);