cdrom: Make device operations read-only

Since function tables are a common target for attackers, it's best to keep
them in read-only memory. As such, this makes the CDROM device ops tables
const. This drops additionally n_minors, since it isn't used meaningfully,
and sets the only user of cdrom_dummy_generic_packet explicitly so the
variables can all be const.

Inspired by similar changes in grsecurity/PaX.

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/cdrom/gdrom.c b/drivers/cdrom/gdrom.c
index 46ecd95d7161..1afab6558d0c 100644
--- a/drivers/cdrom/gdrom.c
+++ b/drivers/cdrom/gdrom.c
@@ -481,7 +481,7 @@ static int gdrom_audio_ioctl(struct cdrom_device_info *cdi, unsigned int cmd,
         return -EINVAL;
 }
 
-static struct cdrom_device_ops gdrom_ops = {
+static const struct cdrom_device_ops gdrom_ops = {
         .open                   = gdrom_open,
         .release                = gdrom_release,
         .drive_status           = gdrom_drivestatus,
@@ -489,9 +489,9 @@ static struct cdrom_device_ops gdrom_ops = {
         .get_last_session       = gdrom_get_last_session,
         .reset                  = gdrom_hardreset,
         .audio_ioctl            = gdrom_audio_ioctl,
+        .generic_packet         = cdrom_dummy_generic_packet,
         .capability             = CDC_MULTI_SESSION | CDC_MEDIA_CHANGED |
                                   CDC_RESET | CDC_DRIVE_STATUS | CDC_CD_R,
-        .n_minors               = 1,
 };
 
 static int gdrom_bdops_open(struct block_device *bdev, fmode_t mode)