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Fri, 05 Mar 2021 09:04:38 -0800 (PST) MIME-Version: 1.0 References: <1aa83e48627978de8068d5e3314185f3a0d7a849.1614302398.git.andreyknvl@google.com> In-Reply-To: <1aa83e48627978de8068d5e3314185f3a0d7a849.1614302398.git.andreyknvl@google.com> From: Andrey Konovalov Date: Fri, 5 Mar 2021 18:04:27 +0100 Message-ID: Subject: Re: [PATCH] kasan, mm: fix crash with HW_TAGS and DEBUG_PAGEALLOC To: Andrew Morton Cc: Catalin Marinas , Will Deacon , Vincenzo Frascino , Dmitry Vyukov , Andrey Ryabinin , Alexander Potapenko , Marco Elver , Peter Collingbourne , Evgenii Stepanov , Branislav Rankov , Kevin Brodsky , Christoph Hellwig , kasan-dev , Linux ARM , Linux Memory Management List , LKML Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: n3pt4jzhf1i8fact13hb7n9i8spbg4zh X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C687FA0049C7 Received-SPF: none (google.com>: No applicable sender policy available) receiver=imf24; identity=mailfrom; envelope-from=""; helo=mail-pg1-f177.google.com; client-ip=209.85.215.177 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614963877-722882 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 Fri, Feb 26, 2021 at 2:25 AM 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(). > > Besides fixing the crash, this also makes the annotation order consistent > with debug_pagealloc_map_pages() preceding kasan_alloc_pages(). > > Signed-off-by: Andrey Konovalov > --- > mm/page_alloc.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index c89e7b107514..54bc237fd319 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1311,10 +1311,14 @@ static __always_inline bool free_pages_prepare(struct page *page, > */ > arch_free_page(page, order); > > - debug_pagealloc_unmap_pages(page, 1 << order); > - > + /* > + * With hardware tag-based KASAN, memory tags must be set > + * before unmapping the page with debug_pagealloc. > + */ > kasan_free_nondeferred_pages(page, order, fpi_flags); Looking at this again, I think we need to move kasan_() callback above arch_free_page(), as that can also make the page unavailable. I'll send v2.