libnvdimm: Out of bounds read in __nd_ioctl()

The "cmd" comes from the user and it can be up to 255.  It it's more
than the number of bits in long, it results out of bounds read when we
check test_bit(cmd, &cmd_mask).  The highest valid value for "cmd" is
ND_CMD_CALL (10) so I added a compare against that.

Fixes: 62232e45f4a2 ("libnvdimm: control (ioctl) messages for nvdimm_bus and nvdimm devices")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200225162055.amtosfy7m35aivxg@kili.mountain
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
index a8b5159..09087c3 100644 (file)
--- a/drivers/nvdimm/bus.c
+++ b/drivers/nvdimm/bus.c
@@ -1042,8 +1042,10 @@ static int __nd_ioctl(struct nvdimm_bus *nvdimm_bus, struct nvdimm *nvdimm,
                        return -EFAULT;
        }
 
-       if (!desc || (desc->out_num + desc->in_num == 0) ||
-                       !test_bit(cmd, &cmd_mask))
+       if (!desc ||
+           (desc->out_num + desc->in_num == 0) ||
+           cmd > ND_CMD_CALL ||
+           !test_bit(cmd, &cmd_mask))
                return -ENOTTY;
 
        /* fail write commands (when read-only) */