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[209.85.220.65]) by mx.google.com with SMTPS id k132sor10166831iof.136.2019.07.02.09.57.10 for (Google Transport Security); Tue, 02 Jul 2019 09:57:10 -0700 (PDT) Received-SPF: pass (google.com: domain of henryburns@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=ErLvOg6E; spf=pass (google.com: domain of henryburns@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=henryburns@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=d3ruOHdYru6Rpy+BKpMXi/6c+V83W2zZQqeLjuI07mA=; b=ErLvOg6Ev6zdphtHAlsPI/i4E1PAFFXuaLmpX6JcmhUUgS/xmdRuySXKCpIRtG+kX1 FsBNUdt7zVXIciKH78drKjYo4PYJhD0tQnv5rYwR3/PbGcFitIGiyFOgRNQv0cqHlGeu 9y928edF1AI0QN3d9ySA6ju08SKBpvuUyqAVUUTBKxMF/hoGVeig2TwgtMcmDhk5bwON ytRV6TMwbAXFECT+G69te6UyI4Y/HZtbTAL2PPKYiox8zBVdb6HWzEWgwyGh9YaT0+o5 RvasPdi/clcVZRh3FzLopILMMo7MJkLlQhmUJLYkDyArxNRZCsan6cYz+PMwXxGZXyRc 2XAw== X-Google-Smtp-Source: APXvYqy+XdTH/NEg0tFMMzUuM/+XmEQEFt0V0klg3HtEJYTy61ahf+1pdl0T/rIL9bJh57cA1/DbyP6ClHqPxMl8h3w= X-Received: by 2002:a5d:9e48:: with SMTP id i8mr22818920ioi.51.1562086630549; Tue, 02 Jul 2019 09:57:10 -0700 (PDT) MIME-Version: 1.0 References: <20190701173042.221453-1-henryburns@google.com> In-Reply-To: From: Henry Burns Date: Tue, 2 Jul 2019 09:56:34 -0700 Message-ID: Subject: Re: [PATCH] mm/z3fold: Fix z3fold_buddy_slots use after free To: Vitaly Wool Cc: Andrew Morton , Vitaly Vul , Mike Rapoport , Xidong Wang , Shakeel Butt , Jonathan Adams , Linux-MM , LKML 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 Tue, Jul 2, 2019 at 12:45 AM Vitaly Wool wrote: > > Hi Henry, > > On Mon, Jul 1, 2019 at 8:31 PM Henry Burns wrote: > > > > Running z3fold stress testing with address sanitization > > showed zhdr->slots was being used after it was freed. > > > > z3fold_free(z3fold_pool, handle) > > free_handle(handle) > > kmem_cache_free(pool->c_handle, zhdr->slots) > > release_z3fold_page_locked_list(kref) > > __release_z3fold_page(zhdr, true) > > zhdr_to_pool(zhdr) > > slots_to_pool(zhdr->slots) *BOOM* > > Thanks for looking into this. I'm not entirely sure I'm all for > splitting free_handle() but let me think about it. > > > Instead we split free_handle into two functions, release_handle() > > and free_slots(). We use release_handle() in place of free_handle(), > > and use free_slots() to call kmem_cache_free() after > > __release_z3fold_page() is done. > > A little less intrusive solution would be to move backlink to pool > from slots back to z3fold_header. Looks like it was a bad idea from > the start. > > Best regards, > Vitaly We still want z3fold pages to be movable though. Wouldn't moving the backink to the pool from slots to z3fold_header prevent us from enabling migration?