From patchwork Mon Jul 12 06:07:07 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 473981 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 252E9C07E9B for ; Mon, 12 Jul 2021 07:10:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0CD6461263 for ; Mon, 12 Jul 2021 07:10:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241461AbhGLHNj (ORCPT ); Mon, 12 Jul 2021 03:13:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:46542 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241350AbhGLHMF (ORCPT ); Mon, 12 Jul 2021 03:12:05 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 58D2360FF0; Mon, 12 Jul 2021 07:09:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626073747; bh=y1dDtowXYmNngW7QfUiJrbLSrm7VBAyFVm3SWaHKEDA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gGbU8ZR9s7/zgKGrIX3i8wKS6Lakiw7QgPLU+n/oCY4beowCIRWvqL/+HuNNQnzfQ yRpA6lrVhMPwF0s+b5agIl8XPjVyieihpSE2pmooNA6StV7hmrcfobHMac4q6GHOOc BOujCcX1K9TwQSqI2cbcOUXgLSIICnJ3O/H5WlTE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jan Kara , Dan Williams , Matthew Wilcox , "Aneesh Kumar K.V" , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 5.12 344/700] dax: fix ENOMEM handling in grab_mapping_entry() Date: Mon, 12 Jul 2021 08:07:07 +0200 Message-Id: <20210712061012.882703827@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060924.797321836@linuxfoundation.org> References: <20210712060924.797321836@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jan Kara [ Upstream commit 1a14e3779dd58c16b30e56558146e5cc850ba8b0 ] grab_mapping_entry() has a bug in handling of ENOMEM condition. Suppose we have a PMD entry at index i which we are downgrading to a PTE entry. grab_mapping_entry() will set pmd_downgrade to true, lock the entry, clear the entry in xarray, and decrement mapping->nrpages. The it will call: entry = dax_make_entry(pfn_to_pfn_t(0), flags); dax_lock_entry(xas, entry); which inserts new PTE entry into xarray. However this may fail allocating the new node. We handle this by: if (xas_nomem(xas, mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM)) goto retry; however pmd_downgrade stays set to true even though 'entry' returned from get_unlocked_entry() will be NULL now. And we will go again through the downgrade branch. This is mostly harmless except that mapping->nrpages is decremented again and we temporarily have an invalid entry stored in xarray. Fix the problem by setting pmd_downgrade to false each time we lookup the entry we work with so that it matches the entry we found. Link: https://lkml.kernel.org/r/20210622160015.18004-1-jack@suse.cz Fixes: b15cd800682f ("dax: Convert page fault handlers to XArray") Signed-off-by: Jan Kara Reviewed-by: Dan Williams Cc: Matthew Wilcox Cc: "Aneesh Kumar K.V" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- fs/dax.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/dax.c b/fs/dax.c index df5485b4bddf..d5d7b9393bca 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -488,10 +488,11 @@ static void *grab_mapping_entry(struct xa_state *xas, struct address_space *mapping, unsigned int order) { unsigned long index = xas->xa_index; - bool pmd_downgrade = false; /* splitting PMD entry into PTE entries? */ + bool pmd_downgrade; /* splitting PMD entry into PTE entries? */ void *entry; retry: + pmd_downgrade = false; xas_lock_irq(xas); entry = get_unlocked_entry(xas, order);