Messages in this thread | | | Date | Sun, 5 Apr 2020 18:40:06 +0200 | From | Greg KH <> | Subject | Re: [PATCH] driver core: Fix possible use after free on name |
| |
On Sun, Apr 05, 2020 at 09:05:49AM -0700, zhangfeionline@gmail.com wrote: > From: PengfeiZhang <zhangfeionline@gmail.com> > > __class_create() copies the pointer to the name passed as an > argument only to be used later. But there's a chance the caller > could immediately free the passed string(e.g., local variable). > This could trigger a use after free when we use class name(e.g., > dev_uevent_name()called by device_destroy(),class_create_release()). > > To be on the safe side: duplicate the string with kstrdup_const() > so that if an unaware user passes an address to a stack-allocated > buffer, we won't get the arbitrary name and crash.
Where are you seeing this happen?
> > Signed-off-by: PengfeiZhang <zhangfeionline@gmail.com> > --- > drivers/base/class.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/drivers/base/class.c b/drivers/base/class.c > index bcd410e..770b3b3 100644 > --- a/drivers/base/class.c > +++ b/drivers/base/class.c > @@ -206,6 +206,7 @@ void class_unregister(struct class *cls) > static void class_create_release(struct class *cls) > { > pr_debug("%s called for %s\n", __func__, cls->name); > + kfree_const(cls->name); > kfree(cls); > } > > @@ -227,7 +228,10 @@ struct class *__class_create(struct module *owner, const char *name, > struct lock_class_key *key) > { > struct class *cls; > - int retval; > + int retval = -EINVAL; > + > + if (!name) > + goto done;
This is a new change, who calls this function with name not being set?
> > cls = kzalloc(sizeof(*cls), GFP_KERNEL); > if (!cls) { > @@ -235,18 +239,27 @@ struct class *__class_create(struct module *owner, const char *name, > goto error; > } > > + name = kstrdup_const(name, GFP_KERNEL); > + if (!name) { > + retval = -ENOMEM; > + goto error; > + }
and overwriting the pointer like that is bad-form, try doing something else here instead.
> + > cls->name = name; > cls->owner = owner; > cls->class_release = class_create_release; > > retval = __class_register(cls, key); > if (retval) > - goto error; > + goto error_class_register; > > return cls; > > +error_class_register: > + kfree(cls->name);
kfree_const()?
thanks,
greg k-h
| |