From patchwork Thu Oct 17 14:46:36 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luis Henriques X-Patchwork-Id: 11196269 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9AD11912 for ; Thu, 17 Oct 2019 14:46:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 82C5921D7D for ; Thu, 17 Oct 2019 14:46:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2440334AbfJQOqm (ORCPT ); Thu, 17 Oct 2019 10:46:42 -0400 Received: from mx2.suse.de ([195.135.220.15]:38618 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2403882AbfJQOqm (ORCPT ); Thu, 17 Oct 2019 10:46:42 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 66C19B6AD; Thu, 17 Oct 2019 14:46:38 +0000 (UTC) From: Luis Henriques To: Jeff Layton , Sage Weil , Ilya Dryomov Cc: ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org, Luis Henriques Subject: [PATCH] ceph: Fix use-after-free in __ceph_remove_cap Date: Thu, 17 Oct 2019 15:46:36 +0100 Message-Id: <20191017144636.28617-1-lhenriques@suse.com> MIME-Version: 1.0 Sender: ceph-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org KASAN reports a use-after-free when running xfstest generic/531, with the following trace: [ 293.903362] kasan_report+0xe/0x20 [ 293.903365] rb_erase+0x1f/0x790 [ 293.903370] __ceph_remove_cap+0x201/0x370 [ 293.903375] __ceph_remove_caps+0x4b/0x70 [ 293.903380] ceph_evict_inode+0x4e/0x360 [ 293.903386] evict+0x169/0x290 [ 293.903390] __dentry_kill+0x16f/0x250 [ 293.903394] dput+0x1c6/0x440 [ 293.903398] __fput+0x184/0x330 [ 293.903404] task_work_run+0xb9/0xe0 [ 293.903410] exit_to_usermode_loop+0xd3/0xe0 [ 293.903413] do_syscall_64+0x1a0/0x1c0 [ 293.903417] entry_SYSCALL_64_after_hwframe+0x44/0xa9 This happens because __ceph_remove_cap() may queue a cap release (__ceph_queue_cap_release) which can be scheduled before that cap is removed from the inode list with rb_erase(&cap->ci_node, &ci->i_caps); And, when this finally happens, the use-after-free will occur. This can be fixed by protecting the rb_erase with the s_cap_lock spinlock, which is used by ceph_send_cap_releases(), before the cap is freed. Signed-off-by: Luis Henriques --- fs/ceph/caps.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index d3b9c9d5c1bd..21ee38cabe98 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -1089,13 +1089,13 @@ void __ceph_remove_cap(struct ceph_cap *cap, bool queue_release) } cap->cap_ino = ci->i_vino.ino; - spin_unlock(&session->s_cap_lock); - /* remove from inode list */ rb_erase(&cap->ci_node, &ci->i_caps); if (ci->i_auth_cap == cap) ci->i_auth_cap = NULL; + spin_unlock(&session->s_cap_lock); + if (removed) ceph_put_cap(mdsc, cap);