[PATCH] x86/resctrl: Fix rdt_find_domain() return value checks

[Reinette Chatre]

rdt_find_domain() may return an ERR_PTR(), NULL, or a pointer to struct
rdt_domain. It is thus required that the return value be checked for the
possibility of an ERR_PTR as well as NULL.

In a few instances the return value of rdt_find_domain() is just checked
for NULL - fix these to include a check of ERR_PTR.

Fixes: d89b7379015f ("x86/intel_rdt/cqm: Add mon_data")
Fixes: 521348b011d6 ("x86/intel_rdt: Introduce utility to obtain CDP peer")
Signed-off-by: Reinette Chatre <reinette.cha...@intel.com>
---
Dear Maintainers,

Two original commits are fixed here. d89b7379015f can be found in v4.14 and
521348b011d6 starting in v4.20. I am unsure whether this is appropriate for
stable since it is not fixing an issue reported by users. This issue was
discovered during code inspection.

Thank you

Reinette


 arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 2 +-
 arch/x86/kernel/cpu/resctrl/rdtgroup.c    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c 
b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index 6f7adb3be01e..3b5de7d54307 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -538,7 +538,7 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
 
        r = &rdt_resources_all[resid];
        d = rdt_find_domain(r, domid, NULL);
-       if (!d) {
+       if (IS_ERR_OR_NULL(d)) {
                ret = -ENOENT;
                goto out;
        }
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c 
b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 1c7827d142e7..715c6697b07d 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1029,7 +1029,7 @@ static int rdt_cdp_peer_get(struct rdt_resource *r, 
struct rdt_domain *d,
         * peer RDT CDP resource. Hence the WARN.
         */
        _d_cdp = rdt_find_domain(_r_cdp, d->id, NULL);
-       if (WARN_ON(!_d_cdp)) {
+       if (WARN_ON(IS_ERR_OR_NULL(_d_cdp))) {
                _r_cdp = NULL;
                ret = -EINVAL;
        }
-- 
2.17.0