RDMA/ionic: bound node_desc sysfs read with %.64s

node_desc[64] in struct ib_device is not guaranteed to be NUL-
terminated. The core IB sysfs handler uses "%.64s" for exactly this
reason (drivers/infiniband/core/sysfs.c:1307), since node_desc_store()
performs a raw memcpy of up to IB_DEVICE_NODE_DESC_MAX bytes with no NUL
termination:

  memcpy(desc.node_desc, buf, min_t(int, count, IB_DEVICE_NODE_DESC_MAX));

If exactly 64 bytes are written via the node_desc sysfs file, the array
contains no NUL byte. The ionic hca_type_show() handler uses unbounded
"%s" and will read past the end of node_desc into adjacent fields of
struct ib_device until it encounters a NUL.

ionic supports IB_DEVICE_MODIFY_NODE_DESC, so this is triggerable by
userspace.

Match the core handler and bound the format specifier.

Cc: [email protected]
Fixes: 2075bbe ("RDMA/ionic: Register device ops for miscellaneous functionality")
Link: https://patch.msgid.link/r/CALynFi7NAbhDCt1tdaDbf6TnLvAqbaHa6-Wqf6OkzREbA_PAfg@mail.gmail.com
Signed-off-by: Kai Aizen <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>

Author: IzenJ

drivers/infiniband/hw/ionic/ionic_ibdev.c

@@ -185,7 +185,7 @@ static ssize_t hca_type_show(struct device *device,
 	struct ionic_ibdev *dev =
 		rdma_device_to_drv_device(device, struct ionic_ibdev, ibdev);
 
-	return sysfs_emit(buf, "%s\n", dev->ibdev.node_desc);
+	return sysfs_emit(buf, "%s.64\n", dev->ibdev.node_desc);
 }
 static DEVICE_ATTR_RO(hca_type);