| From 7322f514f8c0afbf89c11728d7c15708b1b8ed37 Mon Sep 17 00:00:00 2001 |
| From: Xiaochen Shen <xiaochen.shen@intel.com> |
| Date: Tue, 29 Oct 2019 13:25:02 +0800 |
| Subject: [PATCH] x86/resctrl: Prevent NULL pointer dereference when reading |
| mondata |
| |
| commit 26467b0f8407cbd628fa5b7bcfd156e772004155 upstream. |
| |
| 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(). |
| |
| Check '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@intel.com> |
| Signed-off-by: Borislav Petkov <bp@suse.de> |
| Reviewed-by: Fenghua Yu <fenghua.yu@intel.com> |
| Reviewed-by: Tony Luck <tony.luck@intel.com> |
| Cc: "H. Peter Anvin" <hpa@zytor.com> |
| Cc: Ingo Molnar <mingo@redhat.com> |
| Cc: pei.p.jia@intel.com |
| Cc: Reinette Chatre <reinette.chatre@intel.com> |
| Cc: Thomas Gleixner <tglx@linutronix.de> |
| Cc: x86-ml <x86@kernel.org> |
| Link: https://lkml.kernel.org/r/1572326702-27577-1-git-send-email-xiaochen.shen@intel.com |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| 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; |
| -- |
| 2.7.4 |
| |