From bf563b01c2895a4bfd1a29cc5abc67fe706ecffd Mon Sep 17 00:00:00 2001
From: Nicolai Stange <nstange@suse.de>
Date: Mon, 11 Sep 2017 09:45:42 +0200
Subject: [PATCH] driver core: platform: Don't read past the end of "driver_override" buffer
Git-commit: bf563b01c2895a4bfd1a29cc5abc67fe706ecffd
Patch-mainline: v4.14-rc4
References: bsc#1051510

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@vger.kernel.org	# v3.17+
Signed-off-by: Nicolai Stange <nstange@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/base/platform.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -868,7 +868,8 @@ static ssize_t driver_override_store(str
 	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);