[PATCH] scsi: ufs: Fix unexpected values get from ufshcd_read_desc_param()

[Can Guo]

Since WB feature has been added, WB related sysfs entries can be accessed
even when an UFS device does not support WB feature. In that case, the
descriptors which are not supported by the UFS device may be wrongly
reported when they are accessed from their corrsponding sysfs entries.
Fix it by adding a sanity check of parameter offset against the actual
decriptor length.

Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index a2ebcc8..8861ad6 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -3184,13 +3184,19 @@ int ufshcd_read_desc_param(struct ufs_hba *hba,
 	/* Get the length of descriptor */
 	ufshcd_map_desc_id_to_length(hba, desc_id, &buff_len);
 	if (!buff_len) {
-		dev_err(hba->dev, "%s: Failed to get desc length", __func__);
+		dev_err(hba->dev, "%s: Failed to get desc length\n", __func__);
+		return -EINVAL;
+	}
+
+	if (param_offset >= buff_len)
+		dev_err(hba->dev, "%s: Invalid offset 0x%x in descriptor IDN 0x%x, length 0x%x\n",
+			__func__, param_offset, desc_id, buff_len);
 		return -EINVAL;
 	}
 
 	/* Check whether we need temp memory */
 	if (param_offset != 0 || param_size < buff_len) {
-		desc_buf = kmalloc(buff_len, GFP_KERNEL);
+		desc_buf = kzalloc(buff_len, GFP_KERNEL);
 		if (!desc_buf)
 			return -ENOMEM;
 	} else {
@@ -3204,14 +3210,14 @@ int ufshcd_read_desc_param(struct ufs_hba *hba,
 					desc_buf, &buff_len);
 
 	if (ret) {
-		dev_err(hba->dev, "%s: Failed reading descriptor. desc_id %d, desc_index %d, param_offset %d, ret %d",
+		dev_err(hba->dev, "%s: Failed reading descriptor. desc_id %d, desc_index %d, param_offset %d, ret %d\n",
 			__func__, desc_id, desc_index, param_offset, ret);
 		goto out;
 	}
 
 	/* Sanity check */
 	if (desc_buf[QUERY_DESC_DESC_TYPE_OFFSET] != desc_id) {
-		dev_err(hba->dev, "%s: invalid desc_id %d in descriptor header",
+		dev_err(hba->dev, "%s: invalid desc_id %d in descriptor header\n",
 			__func__, desc_buf[QUERY_DESC_DESC_TYPE_OFFSET]);
 		ret = -EINVAL;
 		goto out;
@@ -3221,12 +3227,12 @@ int ufshcd_read_desc_param(struct ufs_hba *hba,
 	buff_len = desc_buf[QUERY_DESC_LENGTH_OFFSET];
 	ufshcd_update_desc_length(hba, desc_id, desc_index, buff_len);
 
-	/* Check wherher we will not copy more data, than available */
-	if (is_kmalloc && (param_offset + param_size) > buff_len)
-		param_size = buff_len - param_offset;
-
-	if (is_kmalloc)
+	if (is_kmalloc) {
+		/* Make sure we don't copy more data than available */
+		if (param_offset + param_size > buff_len)
+			param_size = buff_len - param_offset;
 		memcpy(param_read_buf, &desc_buf[param_offset], param_size);
+	}
 out:
 	if (is_kmalloc)
 		kfree(desc_buf);
-- 
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