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Subject[PATCH] powerpc: fix use-after-free on fixup_port_irq()
Date
There is a possible use-after-free issue in the fixup_port_irq():

460 static void __init fixup_port_irq(int index,
461 struct device_node *np,
462 struct plat_serial8250_port *port)
463 {
...
469 if (!virq && legacy_serial_infos[index].irq_check_parent) {
470 np = of_get_parent(np); --> modified here.
...
474 of_node_put(np); ---> released here
475 }
...
481 #ifdef CONFIG_SERIAL_8250_FSL
482 if (of_device_is_compatible(np, "fsl,ns16550")) --> dereferenced here
...
484 #endif
485 }

We solve this problem by introducing a new parent_np variable.

Fixes: 9deaa53ac7fa ("serial: add irq handler for Freescale 16550 errata.")
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Rob Herring <robh@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org
---
arch/powerpc/kernel/legacy_serial.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/legacy_serial.c b/arch/powerpc/kernel/legacy_serial.c
index 7cea597..0105f3e 100644
--- a/arch/powerpc/kernel/legacy_serial.c
+++ b/arch/powerpc/kernel/legacy_serial.c
@@ -461,17 +461,18 @@ static void __init fixup_port_irq(int index,
struct device_node *np,
struct plat_serial8250_port *port)
{
+ struct device_node *parent_np;
unsigned int virq;

DBG("fixup_port_irq(%d)\n", index);

virq = irq_of_parse_and_map(np, 0);
if (!virq && legacy_serial_infos[index].irq_check_parent) {
- np = of_get_parent(np);
- if (np == NULL)
+ parent_np = of_get_parent(np);
+ if (parent_np == NULL)
return;
- virq = irq_of_parse_and_map(np, 0);
- of_node_put(np);
+ virq = irq_of_parse_and_map(parent_np, 0);
+ of_node_put(parent_np);
}
if (!virq)
return;
--
2.9.5
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