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

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 <[email protected]>
Signed-off-by: Eli Cohen <[email protected]>
Signed-off-by: Saeed Mahameed <[email protected]>
Reviewed-by: Jacob Keller <[email protected]>

diff --git a/lib/cpu_rmap.c b/lib/cpu_rmap.c
index f08d9c56f712e76c968c31b4195865fb9d5ce3d7..e77f12bb3c7748fa872a730778be9780e8f22e1e 100644 (file)
--- a/lib/cpu_rmap.c
+++ b/lib/cpu_rmap.c
@@ -232,7 +232,8 @@ 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);
@@ -268,6 +269,7 @@ 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);
 }
 
@@ -297,6 +299,7 @@ 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;