Messages in this thread | | | From | 宋牧春 <> | Date | Mon, 6 Apr 2020 19:04:14 +0800 | Subject | Re: [External] Re: [PATCH] driver core: Fix possible use after free on name |
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Hi PengfeiZhang,
Greg KH <gregkh@linuxfoundation.org> 于2020年4月6日周一 上午12:40写道: > > 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
Yeah, you have some problem with this fix patch which Greg mentioned. Can you fix it? And send the fix patch v2 to Greg?
-- Yours, Muchun
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