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From:   Geert Uytterhoeven <geert+renesas@glider.be>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Russell King <linux@armlinux.org.uk>,
        Adrian Salido <salidoa@google.com>,
        Nicolai Stange <nstange@suse.de>,
        Sasha Levin <Alexander.Levin@microsoft.com>,
        Todd Kjos <tkjos@android.com>, linux-kernel@vger.kernel.org,
        Geert Uytterhoeven <geert+renesas@glider.be>
Subject: [PATCH v2 3/4] ARM: amba: Don't read past the end of sysfs "driver_override" buffer
Date:   Tue, 10 Apr 2018 15:21:45 +0200
Message-Id: <1523366506-19832-4-git-send-email-geert+renesas@glider.be>
In-Reply-To: <1523366506-19832-1-git-send-email-geert+renesas@glider.be>
References: <1523366506-19832-1-git-send-email-geert+renesas@glider.be>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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