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Date: Thu, 27 Oct 2022 21:15:54 +0200 From: Andrey Konovalov <andreyknvl@...il.com> To: Kees Cook <keescook@...omium.org> Cc: Christoph Lameter <cl@...ux.com>, Dmitry Vyukov <dvyukov@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, Andrew Morton <akpm@...ux-foundation.org>, Vlastimil Babka <vbabka@...e.cz>, Roman Gushchin <roman.gushchin@...ux.dev>, Hyeonggon Yoo <42.hyeyoo@...il.com>, Andrey Ryabinin <ryabinin.a.a@...il.com>, Alexander Potapenko <glider@...gle.com>, Vincenzo Frascino <vincenzo.frascino@....com>, linux-mm@...ck.org, kasan-dev@...glegroups.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH] mm: Make ksize() a reporting-only function On Thu, Oct 27, 2022 at 9:13 PM Kees Cook <keescook@...omium.org> wrote: > > On Thu, Oct 27, 2022 at 09:05:45PM +0200, Andrey Konovalov wrote: > > On Sat, Oct 22, 2022 at 8:08 PM Kees Cook <keescook@...omium.org> wrote: > > [...] > > > -/* Check that ksize() makes the whole object accessible. */ > > > +/* Check that ksize() does NOT unpoison whole object. */ > > > static void ksize_unpoisons_memory(struct kunit *test) > > > { > > > char *ptr; > > > @@ -791,15 +791,17 @@ static void ksize_unpoisons_memory(struct kunit *test) > > > > > > ptr = kmalloc(size, GFP_KERNEL); > > > KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); > > > + > > > real_size = ksize(ptr); > > > + KUNIT_EXPECT_GT(test, real_size, size); > > > > > > OPTIMIZER_HIDE_VAR(ptr); > > > > > > /* This access shouldn't trigger a KASAN report. */ > > > - ptr[size] = 'x'; > > > + ptr[size - 1] = 'x'; > > > > > > /* This one must. */ > > > - KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[real_size]); > > > + KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[real_size - 1]); > > > > How about also accessing ptr[size] here? It would allow for a more > > precise checking of the in-object redzone. > > Sure! Probably both ptr[size] and ptr[real_size -1], yes? Yes, sounds good. Thank you!
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