scsi: scsi_transport_fc: Adjust struct fc_nl_event flex array usage

In order to help the compiler reason about the destination buffer in struct fc_nl_event, add a flexible array member for this purpose. However, since the header is UAPI, it must not change size or layout, so a union is used. The allocation size calculations are also corrected (it was potentially allocating an extra 8 bytes), and the padding is zeroed to avoid leaking kernel heap memory contents. Detected at run-time by the recently added memcpy() bounds checking: memcpy: detected field-spanning write (size 8) of single field "&event->event_data" at drivers/scsi/scsi_transport_fc.c:581 (size 4)

Kees Cook committed 4 years ago

Commit d88a0241 parent 1a2433b2 files · +10 −5Browse files

Showing the changes to include/uapi (1 of 2 files). Show all

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include/uapi/scsi/scsi_netlink_fc.h+5−2

  * FC Transport Broadcast Event Message :
  *   FC_NL_ASYNC_EVENT
  *
- * Note: if Vendor Unique message, &event_data will be  start of
+ * Note: if Vendor Unique message, event_data_flex will be start of
  * 	 vendor unique payload, and the length of the payload is
  *       per event_datalen
  *
 	__u16 event_datalen;
 	__u32 event_num;
 	__u32 event_code;
-	__u32 event_data;
+	union {
+		__u32 event_data;
+		__DECLARE_FLEX_ARRAY(__u8, event_data_flex);
+	};
 } __attribute__((aligned(sizeof(__u64))));