From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BE546C433F5 for ; Mon, 6 Dec 2021 15:05:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347571AbhLFPJH (ORCPT ); Mon, 6 Dec 2021 10:09:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346692AbhLFPG6 (ORCPT ); Mon, 6 Dec 2021 10:06:58 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 47892C07E5F7; Mon, 6 Dec 2021 07:03:11 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 08E88B81018; Mon, 6 Dec 2021 15:03:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 47590C341C5; Mon, 6 Dec 2021 15:03:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1638802988; bh=hKuToEGQdkelpbyquX+wm/ISvQPDg6rdgOlJly+IrOY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sih2tVmx17ohEuTXw/FBXJ4S0TWnpjKMv+2yiM6q6qfXPCOTCiXEvW9pr6HYKKT6c YVDzgXs/idg/++NEzAATVqQKqXvaIGOKSoYOxc0c7cUoxiNPfDqKqd/R/jc8KdaFmj pp9G5UVJuG3toHV1PDa32cc6EeEEL0XsQYd8SsKU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Frank Dinoff , Miklos Szeredi Subject: [PATCH 4.9 09/62] fuse: fix page stealing Date: Mon, 6 Dec 2021 15:55:52 +0100 Message-Id: <20211206145549.480110780@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211206145549.155163074@linuxfoundation.org> References: <20211206145549.155163074@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Miklos Szeredi commit 712a951025c0667ff00b25afc360f74e639dfabe upstream. It is possible to trigger a crash by splicing anon pipe bufs to the fuse device. The reason for this is that anon_pipe_buf_release() will reuse buf->page if the refcount is 1, but that page might have already been stolen and its flags modified (e.g. PG_lru added). This happens in the unlikely case of fuse_dev_splice_write() getting around to calling pipe_buf_release() after a page has been stolen, added to the page cache and removed from the page cache. Fix by calling pipe_buf_release() right after the page was inserted into the page cache. In this case the page has an elevated refcount so any release function will know that the page isn't reusable. Reported-by: Frank Dinoff Link: https://lore.kernel.org/r/CAAmZXrsGg2xsP1CK+cbuEMumtrqdvD-NKnWzhNcvn71RV3c1yw@mail.gmail.com/ Fixes: dd3bb14f44a6 ("fuse: support splice() writing to fuse device") Cc: # v2.6.35 Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman --- fs/fuse/dev.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -898,6 +898,12 @@ static int fuse_try_move_page(struct fus goto out_put_old; } + /* + * Release while we have extra ref on stolen page. Otherwise + * anon_pipe_buf_release() might think the page can be reused. + */ + pipe_buf_release(cs->pipe, buf); + get_page(newpage); if (!(buf->flags & PIPE_BUF_FLAG_LRU)) @@ -2040,8 +2046,12 @@ static ssize_t fuse_dev_splice_write(str pipe_lock(pipe); out_free: - for (idx = 0; idx < nbuf; idx++) - pipe_buf_release(pipe, &bufs[idx]); + for (idx = 0; idx < nbuf; idx++) { + struct pipe_buffer *buf = &bufs[idx]; + + if (buf->ops) + pipe_buf_release(pipe, buf); + } pipe_unlock(pipe); kfree(bufs);