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Message-Id: <1572326702-27577-1-git-send-email-xiaochen.shen@intel.com>
Date: Tue, 29 Oct 2019 13:25:02 +0800
From: Xiaochen Shen <xiaochen.shen@...el.com>
To: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
tony.luck@...el.com, fenghua.yu@...el.com,
reinette.chatre@...el.com
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, pei.p.jia@...el.com,
xiaochen.shen@...el.com
Subject: [PATCH] x86/resctrl: Prevent NULL pointer dereference when reading mondata
When a mon group is being deleted, rdtgrp->flags is set to RDT_DELETED
in rdtgroup_rmdir_mon() firstly. The structure of rdtgrp will be freed
until rdtgrp->waitcount is dropped to 0 in rdtgroup_kn_unlock() later.
During the window of deleting a mon group, if an application calls
rdtgroup_mondata_show() to read mondata under this mon group,
'rdtgrp' returned from rdtgroup_kn_lock_live() is a NULL pointer when
rdtgrp->flags is RDT_DELETED. And then 'rdtgrp' is passed in this path:
rdtgroup_mondata_show() --> mon_event_read() --> mon_event_count().
Thus it results in NULL pointer dereference in mon_event_count().
Add checking of 'rdtgrp' in rdtgroup_mondata_show(), and return -ENOENT
immediately when reading mondata during the window of deleting a mon
group.
Fixes: d89b7379015f ("x86/intel_rdt/cqm: Add mon_data")
Signed-off-by: Xiaochen Shen <xiaochen.shen@...el.com>
Reviewed-by: Fenghua Yu <fenghua.yu@...el.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
---
arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index efbd54cc4e69..055c8613b531 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -522,6 +522,10 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
int ret = 0;
rdtgrp = rdtgroup_kn_lock_live(of->kn);
+ if (!rdtgrp) {
+ ret = -ENOENT;
+ goto out;
+ }
md.priv = of->kn->priv;
resid = md.u.rid;
--
1.8.3.1
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