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authorXiaochen Shen <xiaochen.shen@intel.com>2019-10-29 13:25:02 +0800
committerBorislav Petkov <bp@suse.de>2019-11-03 17:51:22 +0100
commit26467b0f8407cbd628fa5b7bcfd156e772004155 (patch)
treec4dadaeb2273ce7ab55b6716c3336464d0fa222b
parent6fee2a0be0ecae939d4b6cd8297d88b5cbb61654 (diff)
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(). 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
-rw-r--r--arch/x86/kernel/cpu/resctrl/ctrlmondata.c4
1 files changed, 4 insertions, 0 deletions
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;