linux-kernel - [PATCH 3/3] driver core: platform: Don't read past the end of "driver

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Date:   Mon, 11 Sep 2017 09:45:42 +0200
From:   Nicolai Stange <nstange@...e.de>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Adrian Salido <salidoa@...gle.com>,
        Sasha Levin <sasha.levin@...cle.com>,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        Nicolai Stange <nstange@...e.de>
Subject: [PATCH 3/3] driver core: platform: Don't read past the end of "driver_override" buffer

When printing the driver_override parameter when it is 4095 and 4094 bytes
long, the printing code would access invalid memory because we need count+1
bytes for printing.

Reject driver_override values of these lengths in driver_override_store().

This is in close analogy to commit 4efe874aace5 ("PCI: Don't read past the
end of sysfs "driver_override" buffer") from Sasha Levin.

Fixes: 3d713e0e382e ("driver core: platform: add device binding path 'driver_override'")
Cc: stable@...r.kernel.org	# v3.17+
Signed-off-by: Nicolai Stange <nstange@...e.de>
---
 drivers/base/platform.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index d1bd99271066..9045c5f3734e 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -868,7 +868,8 @@ static ssize_t driver_override_store(struct device *dev,
 	struct platform_device *pdev = to_platform_device(dev);
 	char *driver_override, *old, *cp;
 
-	if (count > PATH_MAX)
+	/* We need to keep extra room for a newline */
+	if (count >= (PAGE_SIZE - 1))
 		return -EINVAL;
 
 	driver_override = kstrndup(buf, count, GFP_KERNEL);
-- 
2.13.5