From d2ffed5185df9d8d9ccd150e4340e3b6f96a8381 Mon Sep 17 00:00:00 2001
From: Geert Uytterhoeven <geert+renesas@glider.be>
Date: Tue, 10 Apr 2018 15:21:45 +0200
Subject: [PATCH] ARM: amba: Don't read past the end of sysfs "driver_override" buffer
Git-commit: d2ffed5185df9d8d9ccd150e4340e3b6f96a8381
Patch-mainline: v4.17-rc3
References: CVE-2018-9385,bsc#1100491

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.

Cfr. commits 4efe874aace57dba ("PCI: Don't read past the end of sysfs
"driver_override" buffer") and bf563b01c2895a4b ("driver core: platform:
Don't read past the end of "driver_override" buffer").

Fixes: 3cf385713460eb2b ("ARM: 8256/1: driver coamba: add device binding path 'driver_override'")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Todd Kjos <tkjos@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

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

--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c
@@ -83,7 +83,8 @@ static ssize_t driver_override_store(str
 	struct amba_device *dev = to_amba_device(_dev);
 	char *driver_override, *old = dev->driver_override, *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);