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[209.85.220.65]) by mx.google.com with SMTPS id j6sor32231200iog.11.2019.07.25.00.38.07 for (Google Transport Security); Thu, 25 Jul 2019 00:38:07 -0700 (PDT) Received-SPF: pass (google.com: domain of dvyukov@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=fr9l8juY; spf=pass (google.com: domain of dvyukov@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=dvyukov@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=xNvB2ONftmaWiXRhMLu1nth3BAaraeOQSf/+WChcARs=; b=fr9l8juYjQ/JeEFFeRXMS2hULLCf6FmgD0GiXuRPt9+/6vbFkhv5fQao4HtvkA1nSN Hundf5061xCvw3cztPVqXSkqRTGK2+vMqrMfb6feMfOQ9OzGEep8DHobwE2pjj0luZkN jm4UXpBAwsX5vgWkM5f58ag9ySz5Auqvwhj45Z+rASuMKRl/VGpS3UNX8EE+ii+HoduO j5niOd6+lCwe5LWAv/h2Go0EtQiyr6jxuu2YVp+rAFkGEG1IuRGMMLrQJC0JJlyYGvj4 +3bXp60tPupGxnNuv+VayoQQCoO0u2dT4jt71tRA9pjZUp4TDvss4i/07EobyLH5SMbJ svLw== X-Google-Smtp-Source: APXvYqyTIhEg25V35EKAUow1cficLpe2IWeBlMVkavYr91rSmxFP0dG+elET2304HhNnBYyHzZ/DpaNs09dqyAhP+4Q= X-Received: by 2002:a6b:b556:: with SMTP id e83mr78484315iof.94.1564040286860; Thu, 25 Jul 2019 00:38:06 -0700 (PDT) MIME-Version: 1.0 References: <20190725055503.19507-1-dja@axtens.net> <20190725055503.19507-3-dja@axtens.net> In-Reply-To: <20190725055503.19507-3-dja@axtens.net> From: Dmitry Vyukov Date: Thu, 25 Jul 2019 09:37:55 +0200 Message-ID: Subject: Re: [PATCH 2/3] fork: support VMAP_STACK with KASAN_VMALLOC To: Daniel Axtens Cc: kasan-dev , Linux-MM , "the arch/x86 maintainers" , Andrey Ryabinin , Alexander Potapenko , Andy Lutomirski Content-Type: text/plain; charset="UTF-8" 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 Thu, Jul 25, 2019 at 7:55 AM Daniel Axtens wrote: > > Supporting VMAP_STACK with KASAN_VMALLOC is straightforward: > > - clear the shadow region of vmapped stacks when swapping them in > - tweak Kconfig to allow VMAP_STACK to be turned on with KASAN > > Signed-off-by: Daniel Axtens Reviewed-by: Dmitry Vyukov > --- > arch/Kconfig | 9 +++++---- > kernel/fork.c | 4 ++++ > 2 files changed, 9 insertions(+), 4 deletions(-) > > diff --git a/arch/Kconfig b/arch/Kconfig > index a7b57dd42c26..e791196005e1 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -825,16 +825,17 @@ config HAVE_ARCH_VMAP_STACK > config VMAP_STACK > default y > bool "Use a virtually-mapped stack" > - depends on HAVE_ARCH_VMAP_STACK && !KASAN > + depends on HAVE_ARCH_VMAP_STACK > + depends on !KASAN || KASAN_VMALLOC > ---help--- > Enable this if you want the use virtually-mapped kernel stacks > with guard pages. This causes kernel stack overflows to be > caught immediately rather than causing difficult-to-diagnose > corruption. > > - This is presently incompatible with KASAN because KASAN expects > - the stack to map directly to the KASAN shadow map using a formula > - that is incorrect if the stack is in vmalloc space. > + To use this with KASAN, the architecture must support backing > + virtual mappings with real shadow memory, and KASAN_VMALLOC must > + be enabled. > > config ARCH_OPTIONAL_KERNEL_RWX > def_bool n > diff --git a/kernel/fork.c b/kernel/fork.c > index d8ae0f1b4148..ce3150fe8ff2 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -94,6 +94,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -215,6 +216,9 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) > if (!s) > continue; > > + /* Clear the KASAN shadow of the stack. */ > + kasan_unpoison_shadow(s->addr, THREAD_SIZE); > + > /* Clear stale pointers from reused stack. */ > memset(s->addr, 0, THREAD_SIZE); > > -- > 2.20.1 > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20190725055503.19507-3-dja%40axtens.net.