dm ioctl: validate name length when renaming

When renaming a mapped device validate the length of the new name.

The rename ioctl accepted any correctly-terminated string enclosed
within the data passed from userspace.  The other ioctls enforce a
size limit of DM_NAME_LEN.  If the name is changed and becomes longer
than that, the device can no longer be addressed by name.

Fix it by properly checking for device name length (including
terminating zero).

Cc: stable@kernel.org
Signed-off-by: Milan Broz <mbroz@redhat.com>
Reviewed-by: Jonathan Brassow <jbrassow@redhat.com>
Reviewed-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 54d0588fc1f60fdf40cf10709d4f95961aa1bd8f..977f36612e8374a010fb2447d3743873dc09b97a 100644 (file)
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -704,7 +704,8 @@ static int dev_rename(struct dm_ioctl *param, size_t param_size)
        char *new_name = (char *) param + param->data_start;
 
        if (new_name < param->data ||
-           invalid_str(new_name, (void *) param + param_size)) {
+           invalid_str(new_name, (void *) param + param_size) ||
+           strlen(new_name) > DM_NAME_LEN - 1) {
                DMWARN("Invalid new logical volume name supplied.");
                return -EINVAL;
        }