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[209.85.220.65]) by mx.google.com with SMTPS id x7sor6815888ljj.32.2019.07.02.00.45.57 for (Google Transport Security); Tue, 02 Jul 2019 00:45:58 -0700 (PDT) Received-SPF: pass (google.com: domain of vitalywool@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=d1R5QsTY; spf=pass (google.com: domain of vitalywool@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=vitalywool@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=5IrBPD0J3ThoKKFU4/FQRnog7nkm0QgrOR9tIqfG3FY=; b=d1R5QsTYa5MTtTEHHeCBzlMg9hZoSTCrw52r1zZF5ZH3HtRyfd1fMwfCVSWnHKA2kG 4yOBQgQwFxAfrJAoRCkpslMVYXq4M4qzZEhhN5eAueF6CDd47bf1YGy7CVMb4QD9NZ6N 9FFBS5L6sLobrCnhGda6f/KzikGGytL1t7rQamquIJyhjAVuuWEx7we3wKkf24HvN7Nl 6GDP08kRaJ2X8lBBU/kp/7dw40Kwc2TysdxBYOdxkhkWZwSAlHYNiQ6QQDdXumAjceiA re/bUmjD12UwXfzamlmxA5GbyLp1Ijx3uuJh4MGTHoBwxSrc7K+2vWPk15rDH77JGhPb yT2w== X-Google-Smtp-Source: APXvYqxJ4w6Wee+ZufWo6q87k8jBVJa0des3If6bhXo6eBuX5YbcNlItTrHcH+egqRL+ObwM7oDMNYBaEiKXghKcdow= X-Received: by 2002:a2e:86cc:: with SMTP id n12mr16247419ljj.146.1562053557722; Tue, 02 Jul 2019 00:45:57 -0700 (PDT) MIME-Version: 1.0 References: <20190701173042.221453-1-henryburns@google.com> In-Reply-To: <20190701173042.221453-1-henryburns@google.com> From: Vitaly Wool Date: Tue, 2 Jul 2019 10:45:46 +0300 Message-ID: Subject: Re: [PATCH] mm/z3fold: Fix z3fold_buddy_slots use after free To: Henry Burns Cc: Andrew Morton , Matthew Wilcox , 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: 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