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 3CA14C4332F for ; Wed, 23 Nov 2022 09:56:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237165AbiKWJ4I (ORCPT ); Wed, 23 Nov 2022 04:56:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52344 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237303AbiKWJyz (ORCPT ); Wed, 23 Nov 2022 04:54:55 -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 54DA61165B6; Wed, 23 Nov 2022 01:50:37 -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 DF0E7B81EF6; Wed, 23 Nov 2022 09:50:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EAE34C433D6; Wed, 23 Nov 2022 09:50:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1669197034; bh=UGQq2vAjgVNWPbGeXTGZYDYoRCFJeJBo59GUhShHq8s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MUjFf4JOGRrOSp4A9NYjjGRktjGuVUizrfkaPkjNKPCWlqJxmMZlJTVsL2pIWcAmV EeqlqU3hTLBhrPuo852KJZIEUXGs89udD0JF8XiffZEdn95tDrxYMXEWBb/x5YCbGu FpjamWIlRldQOj+bHRel5Stb9FXYy4C0fLaWqD28= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, George Law , David Howells , Jeff Layton , Jingbo Xu , Matthew Wilcox , linux-cachefs@redhat.com, linux-fsdevel@vger.kernel.org, Sasha Levin Subject: [PATCH 6.0 180/314] netfs: Fix missing xas_retry() calls in xarray iteration Date: Wed, 23 Nov 2022 09:50:25 +0100 Message-Id: <20221123084633.725996799@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221123084625.457073469@linuxfoundation.org> References: <20221123084625.457073469@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: David Howells [ Upstream commit 7e043a80b5dae5c2d2cf84031501de7827fd6c00 ] netfslib has a number of places in which it performs iteration of an xarray whilst being under the RCU read lock. It *should* call xas_retry() as the first thing inside of the loop and do "continue" if it returns true in case the xarray walker passed out a special value indicating that the walk needs to be redone from the root[*]. Fix this by adding the missing retry checks. [*] I wonder if this should be done inside xas_find(), xas_next_node() and suchlike, but I'm told that's not an simple change to effect. This can cause an oops like that below. Note the faulting address - this is an internal value (|0x2) returned from xarray. BUG: kernel NULL pointer dereference, address: 0000000000000402 ... RIP: 0010:netfs_rreq_unlock+0xef/0x380 [netfs] ... Call Trace: netfs_rreq_assess+0xa6/0x240 [netfs] netfs_readpage+0x173/0x3b0 [netfs] ? init_wait_var_entry+0x50/0x50 filemap_read_page+0x33/0xf0 filemap_get_pages+0x2f2/0x3f0 filemap_read+0xaa/0x320 ? do_filp_open+0xb2/0x150 ? rmqueue+0x3be/0xe10 ceph_read_iter+0x1fe/0x680 [ceph] ? new_sync_read+0x115/0x1a0 new_sync_read+0x115/0x1a0 vfs_read+0xf3/0x180 ksys_read+0x5f/0xe0 do_syscall_64+0x38/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae Changes: ======== ver #2) - Changed an unsigned int to a size_t to reduce the likelihood of an overflow as per Willy's suggestion. - Added an additional patch to fix the maths. Fixes: 3d3c95046742 ("netfs: Provide readahead and readpage netfs helpers") Reported-by: George Law Signed-off-by: David Howells Reviewed-by: Jeff Layton Reviewed-by: Jingbo Xu cc: Matthew Wilcox cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/166749229733.107206.17482609105741691452.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/166757987929.950645.12595273010425381286.stgit@warthog.procyon.org.uk/ # v2 Signed-off-by: Sasha Levin --- fs/netfs/buffered_read.c | 9 +++++++-- fs/netfs/io.c | 3 +++ 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c index 0ce535852151..baf668fb4315 100644 --- a/fs/netfs/buffered_read.c +++ b/fs/netfs/buffered_read.c @@ -46,10 +46,15 @@ void netfs_rreq_unlock_folios(struct netfs_io_request *rreq) rcu_read_lock(); xas_for_each(&xas, folio, last_page) { - unsigned int pgpos = (folio_index(folio) - start_page) * PAGE_SIZE; - unsigned int pgend = pgpos + folio_size(folio); + unsigned int pgpos, pgend; bool pg_failed = false; + if (xas_retry(&xas, folio)) + continue; + + pgpos = (folio_index(folio) - start_page) * PAGE_SIZE; + pgend = pgpos + folio_size(folio); + for (;;) { if (!subreq) { pg_failed = true; diff --git a/fs/netfs/io.c b/fs/netfs/io.c index 428925899282..e374767d1b68 100644 --- a/fs/netfs/io.c +++ b/fs/netfs/io.c @@ -121,6 +121,9 @@ static void netfs_rreq_unmark_after_write(struct netfs_io_request *rreq, XA_STATE(xas, &rreq->mapping->i_pages, subreq->start / PAGE_SIZE); xas_for_each(&xas, folio, (subreq->start + subreq->len - 1) / PAGE_SIZE) { + if (xas_retry(&xas, folio)) + continue; + /* We might have multiple writes from the same huge * folio, but we mustn't unlock a folio more than once. */ -- 2.35.1