[PATCH v4 05/14] hw/sd/sdcard: Do not switch to ReceivingData if address is invalid

[Philippe Mathieu-Daudé]

Only move the state machine to ReceivingData if there is no
pending error. This avoids later OOB access while processing
commands queued.

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

  4.3.3 Data Read

  Read command is rejected if BLOCK_LEN_ERROR or ADDRESS_ERROR
  occurred and no data transfer is performed.

  4.3.4 Data Write

  Write command is rejected if BLOCK_LEN_ERROR or ADDRESS_ERROR
  occurred and no data transfer is performed.

WP_VIOLATION errors are not modified: the error bit is set, we
stay in receive-data state, wait for a stop command. All further
data transfer is ignored. See the check on sd->card_status at the
beginning of sd_read_data() and sd_write_data().

Fixes: CVE-2020-13253
Cc: Prasad J Pandit <pjp@fedoraproject.org>
Reported-by: Alexander Bulekov <alxndr@bu.edu>
Buglink: https://bugs.launchpad.net/qemu/+bug/1880822
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
v4: Only modify ADDRESS_ERROR, not WP_VIOLATION (pm215)
---
 hw/sd/sd.c | 34 ++++++++++++++++++++++------------
 1 file changed, 22 insertions(+), 12 deletions(-)

diff --git a/hw/sd/sd.c b/hw/sd/sd.c
index 04451fdad2..7e0d684aca 100644
--- a/hw/sd/sd.c
+++ b/hw/sd/sd.c
@@ -1167,13 +1167,15 @@ static sd_rsp_type_t sd_normal_command(SDState *sd, 
SDRequest req)
     case 17:   /* CMD17:  READ_SINGLE_BLOCK */
         switch (sd->state) {
         case sd_transfer_state:
-            sd->state = sd_sendingdata_state;
-            sd->data_start = addr;
-            sd->data_offset = 0;
 
             if (sd->data_start + sd->blk_len > sd->size) {
                 sd->card_status |= ADDRESS_ERROR;
+                return sd_r1;
             }
+
+            sd->state = sd_sendingdata_state;
+            sd->data_start = addr;
+            sd->data_offset = 0;
             return sd_r1;
 
         default:
@@ -1184,13 +1186,15 @@ static sd_rsp_type_t sd_normal_command(SDState *sd, 
SDRequest req)
     case 18:   /* CMD18:  READ_MULTIPLE_BLOCK */
         switch (sd->state) {
         case sd_transfer_state:
-            sd->state = sd_sendingdata_state;
-            sd->data_start = addr;
-            sd->data_offset = 0;
 
             if (sd->data_start + sd->blk_len > sd->size) {
                 sd->card_status |= ADDRESS_ERROR;
+                return sd_r1;
             }
+
+            sd->state = sd_sendingdata_state;
+            sd->data_start = addr;
+            sd->data_offset = 0;
             return sd_r1;
 
         default:
@@ -1230,14 +1234,17 @@ static sd_rsp_type_t sd_normal_command(SDState *sd, 
SDRequest req)
             /* Writing in SPI mode not implemented.  */
             if (sd->spi)
                 break;
+
+            if (sd->data_start + sd->blk_len > sd->size) {
+                sd->card_status |= ADDRESS_ERROR;
+                return sd_r1;
+            }
+
             sd->state = sd_receivingdata_state;
             sd->data_start = addr;
             sd->data_offset = 0;
             sd->blk_written = 0;
 
-            if (sd->data_start + sd->blk_len > sd->size) {
-                sd->card_status |= ADDRESS_ERROR;
-            }
             if (sd_wp_addr(sd, sd->data_start)) {
                 sd->card_status |= WP_VIOLATION;
             }
@@ -1257,14 +1264,17 @@ static sd_rsp_type_t sd_normal_command(SDState *sd, 
SDRequest req)
             /* Writing in SPI mode not implemented.  */
             if (sd->spi)
                 break;
+
+            if (sd->data_start + sd->blk_len > sd->size) {
+                sd->card_status |= ADDRESS_ERROR;
+                return sd_r1;
+            }
+
             sd->state = sd_receivingdata_state;
             sd->data_start = addr;
             sd->data_offset = 0;
             sd->blk_written = 0;
 
-            if (sd->data_start + sd->blk_len > sd->size) {
-                sd->card_status |= ADDRESS_ERROR;
-            }
             if (sd_wp_addr(sd, sd->data_start)) {
                 sd->card_status |= WP_VIOLATION;
             }
-- 
2.21.3