[PATCH] hw/sd/sdcard: Restrict Class 6 commands to SCSD cards

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

Only SCSD cards support Class 6 (Block Oriented Write Protection)
commands.

  "SD Specifications Part 1 Physical Layer Simplified Spec. v3.01"

  4.3.14 Command Functional Difference in Card Capacity Types

  * Write Protected Group

  SDHC and SDXC do not support write-protected groups. Issuing
  CMD28, CMD29 and CMD30 generates the ILLEGAL_COMMAND error.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
This patch doesn't fix CVE-2020-13253, but greatly reduce
QEMU exposure to it.
https://bugs.launchpad.net/qemu/+bug/1880822
---
 hw/sd/sd.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/sd/sd.c b/hw/sd/sd.c
index 3c06a0ac6d..da39590f58 100644
--- a/hw/sd/sd.c
+++ b/hw/sd/sd.c
@@ -905,6 +905,11 @@ static sd_rsp_type_t sd_normal_command(SDState *sd, SDRequest req)
         sd->multi_blk_cnt = 0;
     }
 
+    if (sd_cmd_class[req.cmd] == 6 && FIELD_EX32(sd->ocr, OCR, CARD_CAPACITY)) {
+        /* Only Standard Capacity cards support class 6 commands */
+        return sd_illegal;
+    }
+
     switch (req.cmd) {
     /* Basic commands (Class 0 and Class 1) */
     case 0:	/* CMD0:   GO_IDLE_STATE */
-- 
2.21.3