From: Xiaochen Shen xiaochen.shen@intel.com
[ Upstream commit 26467b0f8407cbd628fa5b7bcfd156e772004155 ]
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@in... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c index c8b72aff55e00..2052e1e6a11c9 100644 --- a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c +++ b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c @@ -459,6 +459,10 @@ 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;