MM-20934: Fixing int overflow in 32 bits on MaxImageSize check (#14280)

* MM-20934: Fixing int overflow in 32 bits on MaxImageSize check

* Adding comments explaining the casting and the bug fixed there

* Apply suggestions from code review

Co-Authored-By: Juho Nurminen <juhonurm@gmail.com>

* Fixing store layers

Co-authored-by: Juho Nurminen <juhonurm@gmail.com>

app/user.go

@@ -833,7 +833,10 @@ func (a *App) SetProfileImageFromMultiPartFile(userId string, file multipart.Fil
 	if err != nil {
 		return model.NewAppError("SetProfileImage", "api.user.upload_profile_user.decode_config.app_error", nil, err.Error(), http.StatusBadRequest)
 	}
-	if config.Width*config.Height > model.MaxImageSize {
+	// This casting is done to prevent overflow on 32 bit systems (not needed
+	// in 64 bits systems because images can't have more than 32 bits height or
+	// width)
+	if int64(config.Width)*int64(config.Height) > model.MaxImageSize {
 		return model.NewAppError("SetProfileImage", "api.user.upload_profile_user.too_large.app_error", nil, "", http.StatusBadRequest)
 	}