[PATCH v2] accel/qaic: Address potential out-of-bounds read in resp_worker()

Although 'commit 2feec5ae5df7 ("accel/qaic: Handle DBC deactivation if the
owner went away")' fixes the scenario it was intended for by walking the
message and only decoding QAIC_TRANS_DEACTIVATE_FROM_DEV, if present, it
skipped over the bounds checking code that is included in decode_message().
This could lead to issues such as reading past the slab allocation's end,
infinite loops or kernel panics. For those issues to happen, a malformed
wire message is needed to be sent from the device.

Instead of duplicating the bounds checking code already present in
decode_message(), use the function inside resp_worker().

Reported-by: Ruikai Peng <[email protected]>
Fixes: 2feec5ae5df7 ("accel/qaic: Handle DBC deactivation if the owner went away")
Reviewed-by: Jeff Hugo <[email protected]>
Reviewed-by: Lizhi Hou <[email protected]>
Signed-off-by: Youssef Samir <[email protected]>
---
Changes in V2:
- Remove references to tracepoints that are not upstreamed yet, which
  caused merge conflicts
- Link to V1: https://lore.kernel.org/all/[email protected]
---
 drivers/accel/qaic/qaic_control.c | 46 ++++++++++++++++---------------
 1 file changed, 24 insertions(+), 22 deletions(-)

diff --git a/drivers/accel/qaic/qaic_control.c b/drivers/accel/qaic/qaic_control.c
index bb94d3556904..ecbafab7187c 100644
--- a/drivers/accel/qaic/qaic_control.c
+++ b/drivers/accel/qaic/qaic_control.c
@@ -963,11 +963,13 @@ static int decode_status(struct qaic_device *qdev, void *trans, struct manage_ms
 
 static int decode_message(struct qaic_device *qdev, struct manage_msg *user_msg,
 			  struct wire_msg *msg, struct ioctl_resources *resources,
-			  struct qaic_user *usr)
+			  struct qaic_user *usr, bool orphaned_deactivate)
 {
+	u32 msg_hdr_count = le32_to_cpu(msg->hdr.count);
 	u32 msg_hdr_len = le32_to_cpu(msg->hdr.len);
 	struct wire_trans_hdr *trans_hdr;
 	u32 msg_len = 0;
+	int trans_type;
 	int ret;
 	int i;
 
@@ -975,10 +977,12 @@ static int decode_message(struct qaic_device *qdev, struct manage_msg *user_msg,
 	    msg_hdr_len > QAIC_MANAGE_MAX_MSG_LENGTH)
 		return -EINVAL;
 
-	user_msg->len = 0;
-	user_msg->count = le32_to_cpu(msg->hdr.count);
+	if (user_msg) {
+		user_msg->len = 0;
+		user_msg->count = msg_hdr_count;
+	}
 
-	for (i = 0; i < user_msg->count; ++i) {
+	for (i = 0; i < msg_hdr_count; ++i) {
 		u32 hdr_len;
 
 		if (msg_len > msg_hdr_len - sizeof(*trans_hdr))
@@ -990,7 +994,20 @@ static int decode_message(struct qaic_device *qdev, struct manage_msg *user_msg,
 		    size_add(msg_len, hdr_len) > msg_hdr_len)
 			return -EINVAL;
 
-		switch (le32_to_cpu(trans_hdr->type)) {
+		trans_type = le32_to_cpu(trans_hdr->type);
+		/*
+		 * orphaned_deactivate is the case where a deactivate response
+		 * is received from the device after the user owning the DBC,
+		 * and the message requesting deactivation, has gone away.
+		 * In this case, only process QAIC_TRANS_DEACTIVATE_FROM_DEV
+		 * transaction and skip the others.
+		 */
+		if (orphaned_deactivate && trans_type != QAIC_TRANS_DEACTIVATE_FROM_DEV) {
+			msg_len += hdr_len;
+			continue;
+		}
+
+		switch (trans_type) {
 		case QAIC_TRANS_PASSTHROUGH_FROM_DEV:
 			ret = decode_passthrough(qdev, trans_hdr, user_msg, &msg_len);
 			break;
@@ -1281,7 +1298,7 @@ static int qaic_manage(struct qaic_device *qdev, struct qaic_user *usr, struct m
 		goto dma_cont_failed;
 	}
 
-	ret = decode_message(qdev, user_msg, rsp, &resources, usr);
+	ret = decode_message(qdev, user_msg, rsp, &resources, usr, false);
 
 dma_cont_failed:
 	free_dbc_buf(qdev, &resources);
@@ -1446,22 +1463,7 @@ static void resp_worker(struct work_struct *work)
 		 * response to the QAIC_TRANS_TERMINATE_TO_DEV transaction,
 		 * otherwise, the user can issue an soc_reset to the device.
 		 */
-		u32 msg_count = le32_to_cpu(msg->hdr.count);
-		u32 msg_len = le32_to_cpu(msg->hdr.len);
-		u32 len = 0;
-		int j;
-
-		for (j = 0; j < msg_count && len < msg_len; ++j) {
-			struct wire_trans_hdr *trans_hdr;
-
-			trans_hdr = (struct wire_trans_hdr *)(msg->data + len);
-			if (le32_to_cpu(trans_hdr->type) == QAIC_TRANS_DEACTIVATE_FROM_DEV) {
-				if (decode_deactivate(qdev, trans_hdr, &len, NULL))
-					len += le32_to_cpu(trans_hdr->len);
-			} else {
-				len += le32_to_cpu(trans_hdr->len);
-			}
-		}
+		decode_message(qdev, NULL, msg, NULL, NULL, true);
 		/* request must have timed out, drop packet */
 		kfree(msg);
 	}
-- 
2.43.0