linux-kernel - [PATCH] hwrng: geode: fix accessing registers

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Date:   Sun, 10 Sep 2023 10:34:17 +0200
From:   Jonas Gorski <jonas.gorski@...il.com>
To:     Andres Salomon <dilinger@...ued.net>,
        Olivia Mackall <olivia@...enic.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Xiongfeng Wang <wangxiongfeng2@...wei.com>
Cc:     "Timur I . Davletshin" <timur.davletshin@...il.com>,
        Jo-Philipp Wich <jo@...n.io>, linux-geode@...ts.infradead.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] hwrng: geode: fix accessing registers

When the membase and pci_dev pointer were moved to a new struct in priv,
the actual membase users were left untouched, and they started reading
out arbitrary memory behind the struct instead of registers. This
unfortunately turned the RNG into a constant number generator, depending
on the content of what was at that offset.

To fix this, update geode_rng_data_{read,present}() to also get the
membase via amd_geode_priv, and properly read from the right addresses
again.

Fixes: 9f6ec8dc574e ("hwrng: geode - Fix PCI device refcount leak")
Reported-by: Timur I. Davletshin <timur.davletshin@...il.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217882
Tested-by: Timur I. Davletshin <timur.davletshin@...il.com>
Suggested-by: Jo-Philipp Wich <jo@...n.io>
Signed-off-by: Jonas Gorski <jonas.gorski@...il.com>
---
 drivers/char/hw_random/geode-rng.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/char/hw_random/geode-rng.c b/drivers/char/hw_random/geode-rng.c
index 12fbe8091831..159baf00a867 100644
--- a/drivers/char/hw_random/geode-rng.c
+++ b/drivers/char/hw_random/geode-rng.c
@@ -58,7 +58,8 @@ struct amd_geode_priv {
 
 static int geode_rng_data_read(struct hwrng *rng, u32 *data)
 {
-	void __iomem *mem = (void __iomem *)rng->priv;
+	struct amd_geode_priv *priv = (struct amd_geode_priv *)rng->priv;
+	void __iomem *mem = priv->membase;
 
 	*data = readl(mem + GEODE_RNG_DATA_REG);
 
@@ -67,7 +68,8 @@ static int geode_rng_data_read(struct hwrng *rng, u32 *data)
 
 static int geode_rng_data_present(struct hwrng *rng, int wait)
 {
-	void __iomem *mem = (void __iomem *)rng->priv;
+	struct amd_geode_priv *priv = (struct amd_geode_priv *)rng->priv;
+	void __iomem *mem = priv->membase;
 	int data, i;
 
 	for (i = 0; i < 20; i++) {
-- 
2.34.1