On Thu, Feb 20, 2014 at 01:17:44PM -0500, Rik van Riel wrote: > On 02/20/2014 01:14 PM, Dave Jones wrote: > > On Thu, Feb 20, 2014 at 06:44:59PM +0100, Mateusz Guzik wrote: > > > In use after free situations, it is possible for one thread to write to > > > memory that has just been reallocated to a new user. This could open up > > > potential security issues. > > > > > > diff --git a/include/linux/kref.h b/include/linux/kref.h > > > index 484604d..c3f8a0a 100644 > > > --- a/include/linux/kref.h > > > +++ b/include/linux/kref.h > > > @@ -43,8 +43,10 @@ static inline void kref_get(struct kref *kref) > > > /* If refcount was 0 before incrementing then we have a race > > > * condition when this kref is freeing by some other thread > > right now. > > > * In this case one should use kref_get_unless_zero() > > > + * > > > + * Terminate the current thread to stop potential security > > exploits. > > > */ > > > - WARN_ON_ONCE(atomic_inc_return(&kref->refcount) < 2); > > > + BUG_ON(atomic_inc_return(&kref->refcount) < 2); > > > > This isn't "terminating the thread", this is "lock up the box". > > Only if kref_get holds a lock while encountering a refcount > underflow, right? >
Yes, and in a quick glance through the tree it seems we have several codesites where we can find such condition likely to happen, unfortunately. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
