[PATCH v2 52/63] cm4000_cs: Use struct_group() to zero struct cm4000_dev region

Kees Cook
2021-08-18T06:24:17Z

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
---
drivers/char/pcmcia/cm4000_cs.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/char/pcmcia/cm4000_cs.c b/drivers/char/pcmcia/cm4000_cs.c
index 8f1bce0b4fe5..2f43e7088e16 100644
--- 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;
--
2.30.2