cm4000_cs: Use struct_group() to zero struct cm4000_dev region

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Add struct_group() to mark region of struct cm4000_dev that should be
initialized to zero.

Cc: Harald Welte <laforge@gnumonks.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/lkml/YQDvxAofJlI1JoGZ@kroah.com

diff --git a/drivers/char/pcmcia/cm4000_cs.c b/drivers/char/pcmcia/cm4000_cs.c
index 8f1bce0..adaec8f 100644 (file)
--- a/drivers/char/pcmcia/cm4000_cs.c
+++ b/drivers/char/pcmcia/cm4000_cs.c
@@ -116,8 +116,9 @@ struct cm4000_dev {
        wait_queue_head_t atrq;         /* wait for ATR valid */
        wait_queue_head_t readq;        /* used by write to wake blk.read */
 
-       /* warning: do not move this fields.
+       /* warning: do not move this struct group.
         * initialising to zero depends on it - see ZERO_DEV below.  */
+       struct_group(init,
        unsigned char atr_csum;
        unsigned char atr_len_retry;
        unsigned short atr_len;
@@ -140,12 +141,10 @@ struct cm4000_dev {
 
        struct timer_list timer;        /* used to keep monitor running */
        int monitor_running;
+       );
 };
 
-#define        ZERO_DEV(dev)                                           \
-       memset(&dev->atr_csum,0,                                \
-               sizeof(struct cm4000_dev) -                     \
-               offsetof(struct cm4000_dev, atr_csum))
+#define        ZERO_DEV(dev)   memset(&((dev)->init), 0, sizeof((dev)->init))
 
 static struct pcmcia_device *dev_table[CM4000_MAX_DEV];
 static struct class *cmm_class;