media: [PATCH] pci: atomisp_cmd: fix three missing checks on list iterator

The three bugs are here:
	__func__, s3a_buf->s3a_data->exp_id);
	__func__, md_buf->metadata->exp_id);
	__func__, dis_buf->dis_data->exp_id);

The list iterator 's3a_buf/md_buf/dis_buf' will point to a bogus
position containing HEAD if the list is empty or no element is found.
This case must be checked before any use of the iterator, otherwise
it will lead to a invalid memory access.

To fix this bug, add an check. Use a new variable '*_iter' as the
list iterator, while use the old variable '*_buf' as a dedicated
pointer to point to the found element.

Link: https://lore.kernel.org/linux-media/20220414041415.3342-1-xiam0nd.tong@gmail.com
Cc: stable@vger.kernel.org
Fixes: ad85094b ("Revert "media: staging: atomisp: Remove driver"")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/staging/media/atomisp/pci/atomisp_cmd.c

@@ -900,9 +900,9 @@ void atomisp_buf_done(struct atomisp_sub_device *asd, int error,
 	int err;
 	unsigned long irqflags;
 	struct ia_css_frame *frame = NULL;
-	struct atomisp_s3a_buf *s3a_buf = NULL, *_s3a_buf_tmp;
-	struct atomisp_dis_buf *dis_buf = NULL, *_dis_buf_tmp;
-	struct atomisp_metadata_buf *md_buf = NULL, *_md_buf_tmp;
+	struct atomisp_s3a_buf *s3a_buf = NULL, *_s3a_buf_tmp, *s3a_iter;
+	struct atomisp_dis_buf *dis_buf = NULL, *_dis_buf_tmp, *dis_iter;
+	struct atomisp_metadata_buf *md_buf = NULL, *_md_buf_tmp, *md_iter;
 	enum atomisp_metadata_type md_type;
 	struct atomisp_device *isp = asd->isp;
 	struct v4l2_control ctrl;
@@ -941,60 +941,75 @@ void atomisp_buf_done(struct atomisp_sub_device *asd, int error,
 
 	switch (buf_type) {
 	case IA_CSS_BUFFER_TYPE_3A_STATISTICS:
-		list_for_each_entry_safe(s3a_buf, _s3a_buf_tmp,
+		list_for_each_entry_safe(s3a_iter, _s3a_buf_tmp,
 					 &asd->s3a_stats_in_css, list) {
-			if (s3a_buf->s3a_data ==
+			if (s3a_iter->s3a_data ==
 			    buffer.css_buffer.data.stats_3a) {
-				list_del_init(&s3a_buf->list);
-				list_add_tail(&s3a_buf->list,
+				list_del_init(&s3a_iter->list);
+				list_add_tail(&s3a_iter->list,
 					      &asd->s3a_stats_ready);
+				s3a_buf = s3a_iter;
 				break;
 			}
 		}
 
 		asd->s3a_bufs_in_css[css_pipe_id]--;
 		atomisp_3a_stats_ready_event(asd, buffer.css_buffer.exp_id);
-		dev_dbg(isp->dev, "%s: s3a stat with exp_id %d is ready\n",
-			__func__, s3a_buf->s3a_data->exp_id);
+		if (s3a_buf)
+			dev_dbg(isp->dev, "%s: s3a stat with exp_id %d is ready\n",
+				__func__, s3a_buf->s3a_data->exp_id);
+		else
+			dev_dbg(isp->dev, "%s: s3a stat is ready with no exp_id found\n",
+				__func__);
 		break;
 	case IA_CSS_BUFFER_TYPE_METADATA:
 		if (error)
 			break;
 
 		md_type = atomisp_get_metadata_type(asd, css_pipe_id);
-		list_for_each_entry_safe(md_buf, _md_buf_tmp,
+		list_for_each_entry_safe(md_iter, _md_buf_tmp,
 					 &asd->metadata_in_css[md_type], list) {
-			if (md_buf->metadata ==
+			if (md_iter->metadata ==
 			    buffer.css_buffer.data.metadata) {
-				list_del_init(&md_buf->list);
-				list_add_tail(&md_buf->list,
+				list_del_init(&md_iter->list);
+				list_add_tail(&md_iter->list,
 					      &asd->metadata_ready[md_type]);
+				md_buf = md_iter;
 				break;
 			}
 		}
 		asd->metadata_bufs_in_css[stream_id][css_pipe_id]--;
 		atomisp_metadata_ready_event(asd, md_type);
-		dev_dbg(isp->dev, "%s: metadata with exp_id %d is ready\n",
-			__func__, md_buf->metadata->exp_id);
+		if (md_buf)
+			dev_dbg(isp->dev, "%s: metadata with exp_id %d is ready\n",
+				__func__, md_buf->metadata->exp_id);
+		else
+			dev_dbg(isp->dev, "%s: metadata is ready with no exp_id found\n",
+				__func__);
 		break;
 	case IA_CSS_BUFFER_TYPE_DIS_STATISTICS:
-		list_for_each_entry_safe(dis_buf, _dis_buf_tmp,
+		list_for_each_entry_safe(dis_iter, _dis_buf_tmp,
 					 &asd->dis_stats_in_css, list) {
-			if (dis_buf->dis_data ==
+			if (dis_iter->dis_data ==
 			    buffer.css_buffer.data.stats_dvs) {
 				spin_lock_irqsave(&asd->dis_stats_lock,
 						  irqflags);
-				list_del_init(&dis_buf->list);
-				list_add(&dis_buf->list, &asd->dis_stats);
+				list_del_init(&dis_iter->list);
+				list_add(&dis_iter->list, &asd->dis_stats);
 				asd->params.dis_proj_data_valid = true;
 				spin_unlock_irqrestore(&asd->dis_stats_lock,
 						       irqflags);
+				dis_buf = dis_iter;
 				break;
 			}
 		}
 		asd->dis_bufs_in_css--;
-		dev_dbg(isp->dev, "%s: dis stat with exp_id %d is ready\n",
-			__func__, dis_buf->dis_data->exp_id);
+		if (dis_buf)
+			dev_dbg(isp->dev, "%s: dis stat with exp_id %d is ready\n",
+				__func__, dis_buf->dis_data->exp_id);
+		else
+			dev_dbg(isp->dev, "%s: dis stat is ready with no exp_id found\n",
+				__func__);
 		break;
 	case IA_CSS_BUFFER_TYPE_VF_OUTPUT_FRAME:
 	case IA_CSS_BUFFER_TYPE_SEC_VF_OUTPUT_FRAME: