fix attachment file size limit in server backend (#35519)

fix #35512

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

services/context/api.go

@@ -229,8 +229,7 @@ func APIContexter() func(http.Handler) http.Handler {
 
 			// If request sends files, parse them here otherwise the Query() can't be parsed and the CsrfToken will be invalid.
 			if ctx.Req.Method == http.MethodPost && strings.Contains(ctx.Req.Header.Get("Content-Type"), "multipart/form-data") {
-				if err := ctx.Req.ParseMultipartForm(setting.Attachment.MaxSize << 20); err != nil && !strings.Contains(err.Error(), "EOF") { // 32MB max size
-					ctx.APIErrorInternal(err)
+				if !ctx.ParseMultipartForm() {
 					return
 				}
 			}

services/context/base.go

@@ -4,6 +4,7 @@
 package context
 
 import (
+	"errors"
 	"fmt"
 	"html/template"
 	"io"
@@ -42,6 +43,20 @@ type Base struct {
 	Locale translation.Locale
 }
 
+func (b *Base) ParseMultipartForm() bool {
+	err := b.Req.ParseMultipartForm(32 << 20)
+	if err != nil {
+		// TODO: all errors caused by client side should be ignored (connection closed).
+		if !errors.Is(err, io.EOF) && !errors.Is(err, io.ErrUnexpectedEOF) {
+			// Errors caused by server side (disk full) should be logged.
+			log.Error("Failed to parse request multipart form for %s: %v", b.Req.RequestURI, err)
+		}
+		b.HTTPError(http.StatusInternalServerError, "failed to parse request multipart form")
+		return false
+	}
+	return true
+}
+
 // AppendAccessControlExposeHeaders append headers by name to "Access-Control-Expose-Headers" header
 func (b *Base) AppendAccessControlExposeHeaders(names ...string) {
 	val := b.RespHeader().Get("Access-Control-Expose-Headers")

services/context/context.go

@@ -186,8 +186,7 @@ func Contexter() func(next http.Handler) http.Handler {
 
 			// If request sends files, parse them here otherwise the Query() can't be parsed and the CsrfToken will be invalid.
 			if ctx.Req.Method == http.MethodPost && strings.Contains(ctx.Req.Header.Get("Content-Type"), "multipart/form-data") {
-				if err := ctx.Req.ParseMultipartForm(setting.Attachment.MaxSize << 20); err != nil && !strings.Contains(err.Error(), "EOF") { // 32MB max size
-					ctx.ServerError("ParseMultipartForm", err)
+				if !ctx.ParseMultipartForm() {
 					return
 				}
 			}