From: Xiaochen Shen <xiaochen.shen@intel.com>
To: stable@vger.kernel.org, sashal@kernel.org, gregkh@linuxfoundation.org
Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
hpa@zytor.com, tony.luck@intel.com, fenghua.yu@intel.com,
reinette.chatre@intel.com, x86@kernel.org,
linux-kernel@vger.kernel.org, pei.p.jia@intel.com,
xiaochen.shen@intel.com, Borislav Petkov <bp@suse.de>
Subject: [PATCH 4.14 2/3] x86/resctrl: Fix use-after-free due to inaccurate refcount of rdtgroup
Date: Sun, 2 Feb 2020 06:00:23 +0800 [thread overview]
Message-ID: <1580594423-2821-1-git-send-email-xiaochen.shen@intel.com> (raw)
In-Reply-To: <1578500886-21771-1-git-send-email-xiaochen.shen@intel.com>
commit 074fadee59ee7a9d2b216e9854bd4efb5dad679f upstream.
There is a race condition in the following scenario which results in an
use-after-free issue when reading a monitoring file and deleting the
parent ctrl_mon group concurrently:
Thread 1 calls atomic_inc() to take refcount of rdtgrp and then calls
kernfs_break_active_protection() to drop the active reference of kernfs
node in rdtgroup_kn_lock_live().
In Thread 2, kernfs_remove() is a blocking routine. It waits on all sub
kernfs nodes to drop the active reference when removing all subtree
kernfs nodes recursively. Thread 2 could block on kernfs_remove() until
Thread 1 calls kernfs_break_active_protection(). Only after
kernfs_remove() completes the refcount of rdtgrp could be trusted.
Before Thread 1 calls atomic_inc() and kernfs_break_active_protection(),
Thread 2 could call kfree() when the refcount of rdtgrp (sentry) is 0
instead of 1 due to the race.
In Thread 1, in rdtgroup_kn_unlock(), referring to earlier rdtgrp memory
(rdtgrp->waitcount) which was already freed in Thread 2 results in
use-after-free issue.
Thread 1 (rdtgroup_mondata_show) Thread 2 (rdtgroup_rmdir)
-------------------------------- -------------------------
rdtgroup_kn_lock_live
/*
* kn active protection until
* kernfs_break_active_protection(kn)
*/
rdtgrp = kernfs_to_rdtgroup(kn)
rdtgroup_kn_lock_live
atomic_inc(&rdtgrp->waitcount)
mutex_lock
rdtgroup_rmdir_ctrl
free_all_child_rdtgrp
/*
* sentry->waitcount should be 1
* but is 0 now due to the race.
*/
kfree(sentry)*[1]
/*
* Only after kernfs_remove()
* completes, the refcount of
* rdtgrp could be trusted.
*/
atomic_inc(&rdtgrp->waitcount)
/* kn->active-- */
kernfs_break_active_protection(kn)
rdtgroup_ctrl_remove
rdtgrp->flags = RDT_DELETED
/*
* Blocking routine, wait for
* all sub kernfs nodes to drop
* active reference in
* kernfs_break_active_protection.
*/
kernfs_remove(rdtgrp->kn)
rdtgroup_kn_unlock
mutex_unlock
atomic_dec_and_test(
&rdtgrp->waitcount)
&& (flags & RDT_DELETED)
kernfs_unbreak_active_protection(kn)
kfree(rdtgrp)
mutex_lock
mon_event_read
rdtgroup_kn_unlock
mutex_unlock
/*
* Use-after-free: refer to earlier rdtgrp
* memory which was freed in [1].
*/
atomic_dec_and_test(&rdtgrp->waitcount)
&& (flags & RDT_DELETED)
/* kn->active++ */
kernfs_unbreak_active_protection(kn)
kfree(rdtgrp)
Fix it by moving free_all_child_rdtgrp() to after kernfs_remove() in
rdtgroup_rmdir_ctrl() to ensure it has the accurate refcount of rdtgrp.
Backporting notes:
Since upstream commit fa7d949337cc ("x86/resctrl: Rename and move rdt
files to a separate directory"), the file
arch/x86/kernel/cpu/intel_rdt_rdtgroup.c has been renamed and moved to
arch/x86/kernel/cpu/resctrl/rdtgroup.c.
Apply the change against file arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
for older stable trees.
Upstream commit 17eafd076291 ("x86/intel_rdt: Split resource group
removal in two") moved part of resource group removal code from
rdtgroup_rmdir_mon() into a separate function rdtgroup_ctrl_remove().
Apply the change against original code base of rdtgroup_rmdir_mon() for
older stable trees.
Fixes: f3cbeacaa06e ("x86/intel_rdt/cqm: Add rmdir support")
Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Xiaochen Shen <xiaochen.shen@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1578500886-21771-3-git-send-email-xiaochen.shen@intel.com
---
arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index 7349969..0157496 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -1800,11 +1800,6 @@ static int rdtgroup_rmdir_ctrl(struct kernfs_node *kn, struct rdtgroup *rdtgrp,
closid_free(rdtgrp->closid);
free_rmid(rdtgrp->mon.rmid);
- /*
- * Free all the child monitor group rmids.
- */
- free_all_child_rdtgrp(rdtgrp);
-
list_del(&rdtgrp->rdtgroup_list);
/*
@@ -1814,6 +1809,11 @@ static int rdtgroup_rmdir_ctrl(struct kernfs_node *kn, struct rdtgroup *rdtgrp,
kernfs_get(kn);
kernfs_remove(rdtgrp->kn);
+ /*
+ * Free all the child monitor group rmids.
+ */
+ free_all_child_rdtgrp(rdtgrp);
+
return 0;
}
--
1.8.3.1
next prev parent reply other threads:[~2020-02-01 21:33 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-08 16:28 [PATCH 0/4] Fix use-after-free and deadlock issues Xiaochen Shen
2020-01-08 16:28 ` [PATCH 1/4] x86/resctrl: Fix use-after-free when deleting resource groups Xiaochen Shen
[not found] ` <20200109143629.C6C822077B@mail.kernel.org>
2020-01-14 8:51 ` Xiaochen Shen
2020-01-20 16:47 ` [tip: x86/urgent] " tip-bot2 for Xiaochen Shen
2020-01-08 16:28 ` [PATCH 2/4] x86/resctrl: Fix use-after-free due to inaccurate refcount of rdtgroup Xiaochen Shen
[not found] ` <20200109143631.EF0A42077C@mail.kernel.org>
2020-01-14 9:13 ` Xiaochen Shen
2020-01-20 16:47 ` [tip: x86/urgent] " tip-bot2 for Xiaochen Shen
2020-01-08 16:28 ` [PATCH 3/4] x86/resctrl: Fix a deadlock due to inaccurate active reference of kernfs node Xiaochen Shen
[not found] ` <20200109143630.DD673206ED@mail.kernel.org>
2020-01-14 9:17 ` Xiaochen Shen
2020-01-20 16:47 ` [tip: x86/urgent] x86/resctrl: Fix a deadlock due to inaccurate reference tip-bot2 for Xiaochen Shen
2020-01-08 16:28 ` [PATCH 4/4] x86/resctrl: Clean up unused function parameter in mkdir path Xiaochen Shen
2020-01-20 16:47 ` [tip: x86/urgent] " tip-bot2 for Xiaochen Shen
2020-02-01 21:59 ` [PATCH 4.14 1/3] x86/resctrl: Fix use-after-free when deleting resource groups Xiaochen Shen
2020-02-01 22:00 ` Xiaochen Shen [this message]
2020-02-01 22:00 ` [PATCH 4.14 3/3] x86/resctrl: Fix a deadlock due to inaccurate reference Xiaochen Shen
2020-02-01 22:02 ` [PATCH 4.19 1/3] x86/resctrl: Fix use-after-free when deleting resource groups Xiaochen Shen
2020-02-02 21:56 ` Sasha Levin
2020-02-01 22:03 ` [PATCH 4.19 2/3] x86/resctrl: Fix use-after-free due to inaccurate refcount of rdtgroup Xiaochen Shen
2020-02-01 22:04 ` [PATCH 4.19 3/3] x86/resctrl: Fix a deadlock due to inaccurate reference Xiaochen Shen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1580594423-2821-1-git-send-email-xiaochen.shen@intel.com \
--to=xiaochen.shen@intel.com \
--cc=bp@alien8.de \
--cc=bp@suse.de \
--cc=fenghua.yu@intel.com \
--cc=gregkh@linuxfoundation.org \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pei.p.jia@intel.com \
--cc=reinette.chatre@intel.com \
--cc=sashal@kernel.org \
--cc=stable@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=tony.luck@intel.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).