ARM: amba: Don't read past the end of sysfs "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.

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>

diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
index c77eb6e656462bcbb32f87ed1913d856a804949e..8e6ac30316624356dde7517988d1be0133044053 100644 (file)
--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c
@@ -87,7 +87,8 @@ 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);