Hi Vincent, > Old thread, but I had a look at this the other day and I think I got it > working. Since the entire shadow area is mapped at init, we don't need > to do any mappings later.
Nice!! I've always wanted to get back to this too. > It works both with and without KASAN_VMALLOC. KASAN_STACK works too > after I disabled sanitization of the stacktrace code. All kasan kunit > tests pass and the test_kasan.ko module works too. :-) > The CONFIG_UML checks need to > be replaced with something more appropriate (new config? __weak > functions?) and the free functions should probably be hooked up to > madvise(MADV_DONTNEED) so we discard unused pages in the shadow > mapping. I guess a new config would be most appropriate - that way code can be compiled out accordingly. But I don't know who maintains the KASAN code, I guess have to discuss with them. > Note that there's a KASAN stack-out-of-bounds splat on startup when just > booting UML. That looks like a real (17-year-old) bug, I've posted a > fix for that: > > > https://lore.kernel.org/lkml/20220523140403.2361040-1-vincent.whitchu...@axis.com/ Hah, right, I was wondering how that came up suddenly now... Almost suprised it's just a single bug so far :) > --- a/mm/kasan/shadow.c > +++ b/mm/kasan/shadow.c > @@ -295,8 +295,14 @@ int kasan_populate_vmalloc(unsigned long addr, unsigned > long size) > return 0; > > shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr); > - shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE); > shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size); > + > + if (IS_ENABLED(CONFIG_UML)) { > + __memset(kasan_mem_to_shadow((void *)addr), > KASAN_VMALLOC_INVALID, shadow_end - shadow_start); > + return 0; > + } > If that were if (IS_ENABLED(CONFIG_KASAN_NO_SHADOW_ALLOC)) { ... } (or so) as discussed above, it might be a little more readable, but otherwise it doesn't really seem all _that_ intrusive. I'll give it a spin later. johannes _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um
