hw/i3c/dw-i3c: Fix uninitialized data use in short transfer

Coverity reports that dw_i3c_short_transfer() may pass an
uninitialized buffer to dw_i3c_send().

The immediate cause is the use of `data[len] += arg.byte0`, which
reads from an uninitialized element of the buffer. Replace this with
a simple assignment.

Additionally, avoid calling dw_i3c_send() when the constructed payload
length is zero. In that case the transfer has no data phase, so the
controller can transition to the idle state directly.

This resolves the Coverity UNINIT warning and clarifies the handling
of zero-length short transfers.

Resolves: Coverity CID 1645555
Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Nabih Estefan <nabihestefan@google.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Message-ID: <20260311021319.1053774-1-jamin_lin@aspeedtech.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

diff --git a/hw/i3c/dw-i3c.c b/hw/i3c/dw-i3c.c
index e9bdfd6af2ac6c33f3279e2a6efe10eece334fba..d87d42be891418f1d031c53f0079b88a2cc6baf5 100644 (file)
--- a/hw/i3c/dw-i3c.c
+++ b/hw/i3c/dw-i3c.c
@@ -1213,7 +1213,7 @@ static void dw_i3c_short_transfer(DWI3C *s, DWI3CTransferCmd cmd,
          * ignored.
          */
         if (cmd.dbp) {
-            data[len] += arg.byte0;
+            data[len] = arg.byte0;
             len++;
         }
     }
@@ -1228,10 +1228,16 @@ static void dw_i3c_short_transfer(DWI3C *s, DWI3CTransferCmd cmd,
         len++;
     }
 
-    if (dw_i3c_send(s, data, len, &bytes_sent, is_i2c)) {
-        err = DW_I3C_RESP_QUEUE_ERR_I2C_NACK;
+    if (len > 0) {
+        if (dw_i3c_send(s, data, len, &bytes_sent, is_i2c)) {
+            err = DW_I3C_RESP_QUEUE_ERR_I2C_NACK;
+        } else {
+            /* Only go to an idle state on a successful transfer. */
+            ARRAY_FIELD_DP32(s->regs, PRESENT_STATE, CM_TFR_ST_STATUS,
+                             DW_I3C_TRANSFER_STATE_IDLE);
+        }
     } else {
-        /* Only go to an idle state on a successful transfer. */
+        /* No payload bytes for this short transfer. */
         ARRAY_FIELD_DP32(s->regs, PRESENT_STATE, CM_TFR_ST_STATUS,
                          DW_I3C_TRANSFER_STATE_IDLE);
     }