On Mon, Mar 06, 2017 at 01:58:51PM +0100, Peter Zijlstra wrote: > On Mon, Mar 06, 2017 at 01:50:47PM +0100, Dmitry Vyukov wrote: > > On Mon, Mar 6, 2017 at 1:42 PM, Dmitry Vyukov <[email protected]> wrote: > > > KASAN uses compiler instrumentation to intercept all memory accesses. > > > But it does not see memory accesses done in assembly code. > > > One notable user of assembly code is atomic operations. Frequently, > > > for example, an atomic reference decrement is the last access to an > > > object and a good candidate for a racy use-after-free. > > > > > > Add manual KASAN checks to atomic operations. > > > Note: we need checks only before asm blocks and don't need them > > > in atomic functions composed of other atomic functions > > > (e.g. load-cmpxchg loops). > > > > Peter, also pointed me at arch/x86/include/asm/bitops.h. Will add them in > > v2. > > > > > > static __always_inline void atomic_add(int i, atomic_t *v) > > > { > > > + kasan_check_write(v, sizeof(*v)); > > > asm volatile(LOCK_PREFIX "addl %1,%0" > > > : "+m" (v->counter) > > > : "ir" (i)); > > > So the problem is doing load/stores from asm bits, and GCC > (traditionally) doesn't try and interpret APP asm bits. > > However, could we not write a GCC plugin that does exactly that? > Something that interprets the APP asm bits and generates these KASAN > bits that go with it?
Another suspect is the per-cpu stuff, that's all asm foo as well.
