lib: cpu_rmap: Avoid use after free on rmap->obj array entries

stable inclusion
from stable-v4.19.284
commit d1308bd0b24cb1d78fa2747d5fa3e055cc628a48
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7J5UF
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d1308bd0b24cb1d78fa2747d5fa3e055cc628a48

--------------------------------

[ Upstream commit 4e0473f1 ]

When calling irq_set_affinity_notifier() with NULL at the notify
argument, it will cause freeing of the glue pointer in the
corresponding array entry but will leave the pointer in the array. A
subsequent call to free_irq_cpu_rmap() will try to free this entry again
leading to possible use after free.

Fix that by setting NULL to the array entry and checking that we have
non-zero at the array entry when iterating over the array in
free_irq_cpu_rmap().

The current code does not suffer from this since there are no cases
where irq_set_affinity_notifier(irq, NULL) (note the NULL passed for the
notify arg) is called, followed by a call to free_irq_cpu_rmap() so we
don't hit and issue. Subsequent patches in this series excersize this
flow, hence the required fix.

Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NEli Cohen <elic@nvidia.com>
Signed-off-by: NSaeed Mahameed <saeedm@nvidia.com>
Reviewed-by: NJacob Keller <jacob.e.keller@intel.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NGuo Mengqi <guomengqi3@huawei.com>
Reviewed-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

lib/cpu_rmap.c

@@ -235,7 +235,8 @@ void free_irq_cpu_rmap(struct cpu_rmap *rmap)
 
 	for (index = 0; index < rmap->used; index++) {
 		glue = rmap->obj[index];
-		irq_set_affinity_notifier(glue->notify.irq, NULL);
+		if (glue)
+			irq_set_affinity_notifier(glue->notify.irq, NULL);
 	}
 
 	cpu_rmap_put(rmap);
@@ -271,6 +272,7 @@ static void irq_cpu_rmap_release(struct kref *ref)
 		container_of(ref, struct irq_glue, notify.kref);
 
 	cpu_rmap_put(glue->rmap);
+	glue->rmap->obj[glue->index] = NULL;
 	kfree(glue);
 }
 
@@ -300,6 +302,7 @@ int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq)
 	rc = irq_set_affinity_notifier(irq, &glue->notify);
 	if (rc) {
 		cpu_rmap_put(glue->rmap);
+		rmap->obj[glue->index] = NULL;
 		kfree(glue);
 	}
 	return rc;