lib: cpu_rmap: Fix potential use-after-free in irq_cpu_rmap_release()

irq_cpu_rmap_release() calls cpu_rmap_put(), which may free the rmap.
So we need to clear the pointer to our glue structure in rmap before
doing that, not after.

Fixes: 4e0473f1060a ("lib: cpu_rmap: Avoid use after free on rmap->obj array entries")
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/ZHo0vwquhOy3FaXc@decadent.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/lib/cpu_rmap.c b/lib/cpu_rmap.c
index 73c1636..4c34867 100644 (file)
--- a/lib/cpu_rmap.c
+++ b/lib/cpu_rmap.c
@@ -280,8 +280,8 @@ static void irq_cpu_rmap_release(struct kref *ref)
        struct irq_glue *glue =
                container_of(ref, struct irq_glue, notify.kref);
 
-       cpu_rmap_put(glue->rmap);
        glue->rmap->obj[glue->index] = NULL;
+       cpu_rmap_put(glue->rmap);
        kfree(glue);
 }