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 1B5A0C433F5 for ; Wed, 24 Nov 2021 12:30:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244967AbhKXMeG (ORCPT ); Wed, 24 Nov 2021 07:34:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:42294 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245734AbhKXM3D (ORCPT ); Wed, 24 Nov 2021 07:29:03 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 27F8F6113D; Wed, 24 Nov 2021 12:17:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1637756243; bh=gUpxt3ve1Z2Aoy5XSvItD3V3+Y+Jh3KNP9x37YpbzBI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Rw6LbRAc74nrbCpbBkFglPaTOKJPQzX5IHHKRkQHiPKUpLIz2bdzb2WQBHzexQvuX eRcLfcmG2DYfXQd14bQlVYxIbHO9rHbBjtUyxNVYjQlmHbPc+snUYw6f4Yo2DN9lkM q5Puzu92jSPHLJ9TALWcSLivNUM0rTh2je4YpHoM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Frank Dinoff , Miklos Szeredi Subject: [PATCH 4.14 018/251] fuse: fix page stealing Date: Wed, 24 Nov 2021 12:54:20 +0100 Message-Id: <20211124115710.861588503@linuxfoundation.org> X-Mailer: git-send-email 2.34.0 In-Reply-To: <20211124115710.214900256@linuxfoundation.org> References: <20211124115710.214900256@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 @@ -897,6 +897,12 @@ 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)) @@ -2046,8 +2052,12 @@ 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);