[PATCH] powerpc/83xx: fix use-after-free on mpc831x_usb_cfg()

[PATCH] powerpc/83xx: fix use-after-free on mpc831x_usb_cfg()

[Wen Yang]

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.
This patatch also do some cleanup.

Fixes: fd066e850351 ("powerpc/mpc8308: fix USB DR controller initialization")
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Cc: Scott Wood <oss@buserror.net>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org
---
 arch/powerpc/platforms/83xx/usb.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/platforms/83xx/usb.c b/arch/powerpc/platforms/83xx/usb.c
index 3d247d7..56b36fa 100644
--- a/arch/powerpc/platforms/83xx/usb.c
+++ b/arch/powerpc/platforms/83xx/usb.c
@@ -158,14 +158,11 @@ int mpc831x_usb_cfg(void)
 
 	iounmap(immap);
 
-	of_node_put(immr_node);
-
 	/* Map USB SOC space */
 	ret = of_address_to_resource(np, 0, &res);
-	if (ret) {
-		of_node_put(np);
-		return ret;
-	}
+	if (ret)
+		goto out_put_node;
+
 	usb_regs = ioremap(res.start, resource_size(&res));
 
 	/* Using on-chip PHY */
@@ -174,7 +171,7 @@ int mpc831x_usb_cfg(void)
 		u32 refsel;
 
 		if (of_device_is_compatible(immr_node, "fsl,mpc8308-immr"))
-			goto out;
+			goto out_unmap;
 
 		if (of_device_is_compatible(immr_node, "fsl,mpc8315-immr"))
 			refsel = CONTROL_REFSEL_24MHZ;
@@ -201,8 +198,10 @@ int mpc831x_usb_cfg(void)
 		ret = -EINVAL;
 	}
 
-out:
+out_unmap:
 	iounmap(usb_regs);
+out_put_node:
+	of_node_put(immr_node);
 	of_node_put(np);
 	return ret;
 }
-- 
2.9.5

Re: powerpc/83xx: fix use-after-free on mpc831x_usb_cfg()

[Markus Elfring]

> 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.


I imagine that this commit description can be improved a bit more
(by mentioning the influence of “immr_node”?).
How do you think about to omit the word “We” here?


> This patatch also do some cleanup.


Should the renaming of a jump label be contributed in a separate update
step of a small patch series besides a wording without a typo?

Regards,
Markus