linux-kernel - [PATCH] soc: ux500: do not directly dereference _

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Message-Id: <20221023195711.52515-1-Jason@zx2c4.com>
Date:   Sun, 23 Oct 2022 21:57:11 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     linus.walleij@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>, stable@...r.kernel.org,
        kernel test robot <lkp@...el.com>
Subject: [PATCH] soc: ux500: do not directly dereference __iomem

Sparse reports that calling add_device_randomness() on `uid` is a
violation of address spaces. And indeed the next usage uses readl()
properly, but that was left out when passing it toadd_device_
randomness(). So instead copy the whole thing to the stack first.

Fixes: 4040d10a3d44 ("ARM: ux500: add DB serial number to entropy pool")
Cc: Linus Walleij <linus.walleij@...aro.org>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/all/202210230819.loF90KDh-lkp@intel.com/
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
Untested, but hopefully correct.

 drivers/soc/ux500/ux500-soc-id.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/soc/ux500/ux500-soc-id.c b/drivers/soc/ux500/ux500-soc-id.c
index a9472e0e5d61..27d6e25a0115 100644
--- a/drivers/soc/ux500/ux500-soc-id.c
+++ b/drivers/soc/ux500/ux500-soc-id.c
@@ -167,20 +167,18 @@ ATTRIBUTE_GROUPS(ux500_soc);
 static const char *db8500_read_soc_id(struct device_node *backupram)
 {
 	void __iomem *base;
-	void __iomem *uid;
 	const char *retstr;
+	u32 uid[5];
 
 	base = of_iomap(backupram, 0);
 	if (!base)
 		return NULL;
-	uid = base + 0x1fc0;
+	memcpy_fromio(uid, base + 0x1fc0, sizeof(uid));
 
 	/* Throw these device-specific numbers into the entropy pool */
-	add_device_randomness(uid, 0x14);
+	add_device_randomness(uid, sizeof(uid));
 	retstr = kasprintf(GFP_KERNEL, "%08x%08x%08x%08x%08x",
-			 readl((u32 *)uid+0),
-			 readl((u32 *)uid+1), readl((u32 *)uid+2),
-			 readl((u32 *)uid+3), readl((u32 *)uid+4));
+			   uid[0], uid[1], uid[2], uid[3], uid[4]);
 	iounmap(base);
 	return retstr;
 }
-- 
2.38.1