linux-kernel - [PATCH net] lib: cpu_rmap: Fix potential use-after-free in irq_cpu_rmap

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Message-ID: <ZHo0vwquhOy3FaXc@decadent.org.uk>
Date:   Fri, 2 Jun 2023 20:28:15 +0200
From:   Ben Hutchings <ben@...adent.org.uk>
To:     netdev@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
        Eli Cohen <elic@...dia.com>
Subject: [PATCH net] 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 ...")
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
I noticed this issue when reviewing stable changes.  I haven't tested
the change.

Ben.

 lib/cpu_rmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/cpu_rmap.c b/lib/cpu_rmap.c
index 73c1636b927b..4c348670da31 100644
--- 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);
 }
 

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