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[209.85.220.65]) by mx.google.com with SMTPS id c19sor31139062qkl.84.2019.07.26.16.21.09 for (Google Transport Security); Fri, 26 Jul 2019 16:21:09 -0700 (PDT) Received-SPF: pass (google.com: domain of jwadams@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=pmprGLF2; spf=pass (google.com: domain of jwadams@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=jwadams@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=ds6Pn84xnJTs59aQRjsfc8MfNMObGqVIqTNdYf6jDF8=; b=pmprGLF2LW0+Sp8wpilnKxyQ9fpy3RtVaI/uwKChRR6jU8kYntVB/SBwjs2iJ/Ef8t AgoaxKSIaFJe7S7BnUBMzaU5bXb26v3v8TOCHBgGl7orVWxAEikEx7zs9FYVRZ2Kuhq4 LSTUWhQCKjMaQS5eEZ+BcJitwk4cPKvlrXSZDX1iHbS8B0nL0AA6pOZy4QXcTcQMysE5 AythhYvQwGo01Exhcg+nMLtnS5XdBJBKrjciS0HpJOZvZWTfMOeSAbBRtlq3DFoVJ+4G xBuI0RwArlsSejlPmK0YyqwlQDzixITgfEA6xxl4awy3u7kqIvjgYTSSMEYLmZZ99w5Y y/EA== X-Google-Smtp-Source: APXvYqxKsvOaZxq1HqBf7Rf4YiQTcQkrpQGtj9XSIYZVHNSOdDHelqirkEJK9WTuzvgEgdBC2jX6zOfxq5cVBDabxl8= X-Received: by 2002:a37:9ac9:: with SMTP id c192mr65323076qke.30.1564183268223; Fri, 26 Jul 2019 16:21:08 -0700 (PDT) MIME-Version: 1.0 References: <20190726224810.79660-1-henryburns@google.com> <20190726224810.79660-2-henryburns@google.com> In-Reply-To: <20190726224810.79660-2-henryburns@google.com> From: Jonathan Adams Date: Fri, 26 Jul 2019 16:20:32 -0700 Message-ID: Subject: Re: [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() race condition To: Henry Burns Cc: Vitaly Vul , Andrew Morton , Shakeel Butt , David Howells , Thomas Gleixner , Al Viro , Linux-MM , LKML , stable@vger.kernel.org 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 Fri, Jul 26, 2019 at 3:48 PM Henry Burns wrote: > > The constraint from the zpool use of z3fold_destroy_pool() is there are no > outstanding handles to memory (so no active allocations), but it is possible > for there to be outstanding work on either of the two wqs in the pool. > > Calling z3fold_deregister_migration() before the workqueues are drained > means that there can be allocated pages referencing a freed inode, > causing any thread in compaction to be able to trip over the bad > pointer in PageMovable(). > > Fixes: 1f862989b04a ("mm/z3fold.c: support page migration") > > Signed-off-by: Henry Burns Reviewed-by: Jonathan Adams > Cc: > --- > mm/z3fold.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/z3fold.c b/mm/z3fold.c > index 43de92f52961..ed19d98c9dcd 100644 > --- a/mm/z3fold.c > +++ b/mm/z3fold.c > @@ -817,16 +817,19 @@ static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp, > static void z3fold_destroy_pool(struct z3fold_pool *pool) > { > kmem_cache_destroy(pool->c_handle); > - z3fold_unregister_migration(pool); > > /* > * We need to destroy pool->compact_wq before pool->release_wq, > * as any pending work on pool->compact_wq will call > * queue_work(pool->release_wq, &pool->work). > + * > + * There are still outstanding pages until both workqueues are drained, > + * so we cannot unregister migration until then. > */ > > destroy_workqueue(pool->compact_wq); > destroy_workqueue(pool->release_wq); > + z3fold_unregister_migration(pool); > kfree(pool); > } > > -- > 2.22.0.709.g102302147b-goog >