On Thu, Feb 20, 2014 at 01:14:40PM -0500, 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". >
Well, extent of damage caused by non-panicking BUG_ON (if any) depends on the state when kref_get was executed. However, since this condition is already a sign of big trouble (and a potential exploitation attempt), I think a WARN_ON_ONCE is not sufficient. That said, can you elaborate on your concers? You just don't like that comment, don't want that BUG_ON (want a panic instead) or maybe you don't like the change at all (or something else)? Thanks, -- Mateusz Guzik -- 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/
