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Fri, 05 Mar 2021 15:55:10 -0800 (PST) MIME-Version: 1.0 References: <24cd7db274090f0e5bc3adcdc7399243668e3171.1614987311.git.andreyknvl@google.com> <20210305154956.3bbfcedab3f549b708d5e2fa@linux-foundation.org> In-Reply-To: From: Andrey Konovalov Date: Sat, 6 Mar 2021 00:54:59 +0100 Message-ID: Subject: Re: [PATCH v2] kasan, mm: fix crash with HW_TAGS and DEBUG_PAGEALLOC To: Andrew Morton Cc: Alexander Potapenko , Catalin Marinas , Will Deacon , Vincenzo Frascino , Dmitry Vyukov , Andrey Ryabinin , Marco Elver , Peter Collingbourne , Evgenii Stepanov , Branislav Rankov , Kevin Brodsky , kasan-dev , Linux ARM , Linux Memory Management List , LKML , stable Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: 76mnayria9nsw7xp4i4hmz5sehqm7fg7 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: A1D9E2000396 Received-SPF: none (google.com>: No applicable sender policy available) receiver=imf18; identity=mailfrom; envelope-from=""; helo=mail-pj1-f46.google.com; client-ip=209.85.216.46 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614988511-990595 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sat, Mar 6, 2021 at 12:54 AM Andrey Konovalov wrote: > > On Sat, Mar 6, 2021 at 12:50 AM Andrew Morton wrote: > > > > On Sat, 6 Mar 2021 00:36:33 +0100 Andrey Konovalov wrote: > > > > > Currently, kasan_free_nondeferred_pages()->kasan_free_pages() is called > > > after debug_pagealloc_unmap_pages(). This causes a crash when > > > debug_pagealloc is enabled, as HW_TAGS KASAN can't set tags on an > > > unmapped page. > > > > > > This patch puts kasan_free_nondeferred_pages() before > > > debug_pagealloc_unmap_pages() and arch_free_page(), which can also make > > > the page unavailable. > > > > > > ... > > > > > > --- a/mm/page_alloc.c > > > +++ b/mm/page_alloc.c > > > @@ -1304,6 +1304,12 @@ static __always_inline bool free_pages_prepare(struct page *page, > > > > > > kernel_poison_pages(page, 1 << order); > > > > > > + /* > > > + * With hardware tag-based KASAN, memory tags must be set before the > > > + * page becomes unavailable via debug_pagealloc or arch_free_page. > > > + */ > > > + kasan_free_nondeferred_pages(page, order, fpi_flags); > > > + > > > /* > > > * arch_free_page() can make the page's contents inaccessible. s390 > > > * does this. So nothing which can access the page's contents should > > > @@ -1313,8 +1319,6 @@ static __always_inline bool free_pages_prepare(struct page *page, > > > > > > debug_pagealloc_unmap_pages(page, 1 << order); > > > > > > - kasan_free_nondeferred_pages(page, order, fpi_flags); > > > - > > > return true; > > > } > > > > kasan_free_nondeferred_pages() has only two args in current mainline. > > Ah, yes, forgot to mention: this goes on top of: > > kasan: initialize shadow to TAG_INVALID for SW_TAGS > mm, kasan: don't poison boot memory with tag-based modes > > > > > I fixed that in the obvious manner... > > Thanks! > > If you changed this patch, you'll also need to change the other one though. Nevermind, just realized that this should be a backportable fix :)