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Subject[PATCH] powerpc/prom: fix use-after-free on cpu_to_chip_id()
Date
The np variable is still being used after the of_node_put() call,
which may result in use-after-free.
We fix this issue by calling of_node_put() after the last usage.

Fixes: 3eb906c6b6c1 ("powerpc: Make cpu_to_chip_id() available when SMP=n")
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: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org
---
arch/powerpc/kernel/prom.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 7159e79..ad87b94 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -872,13 +872,15 @@ EXPORT_SYMBOL(of_get_ibm_chip_id);
int cpu_to_chip_id(int cpu)
{
struct device_node *np;
+ int id;

np = of_get_cpu_node(cpu, NULL);
if (!np)
return -1;

+ id = of_get_ibm_chip_id(np);
of_node_put(np);
- return of_get_ibm_chip_id(np);
+ return id;
}
EXPORT_SYMBOL(cpu_to_chip_id);

--
2.9.5
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