[PATCH 3/4] ARM: amba: Don't read past the end of sysfs "driver_override" buffer

From: Geert Uytterhoeven <geert+renesas@glider.be>
To: Russell King <linux@armlinux.org.uk>
Cc: Antonios Motakis <a.motakis@virtualopensystems.com>,
	Adrian Salido <salidoa@google.com>,
	Sasha Levin <sasha.levin@oracle.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-kernel@vger.kernel.org,
	Geert Uytterhoeven <geert+renesas@glider.be>
Subject: [PATCH 3/4] ARM: amba: Don't read past the end of sysfs "driver_override" buffer
Date: Fri, 19 Jan 2018 16:24:09 +0100	[thread overview]
Message-ID: <1516375450-30575-4-git-send-email-geert+renesas@glider.be> (raw)
In-Reply-To: <1516375450-30575-1-git-send-email-geert+renesas@glider.be>

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

diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
index 36c5653ced5742b7..4a3ac31c07d0ee49 100644
--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c
@@ -84,7 +84,8 @@ static ssize_t driver_override_store(struct device *_dev,
 	struct amba_device *dev = to_amba_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);
-- 
2.7.4
