From cbd3eb1cd2368b8d0b5c1eecc905cf1e86a3fa22 Mon Sep 17 00:00:00 2001
From: Ben McClelland <ben.mcclelland@versity.com>
Date: Wed, 9 Jul 2025 15:36:16 -0700
Subject: [PATCH] fix: ListMultipartUploads pagination panic and duplicate
 results

This fixes a panic seen when there were a lot of multipart uploads in the
same bucket requiring multiple paginated responses. for example:
panic: runtime error: index out of range [11455] with length 1000
goroutine 418 [running]:
github.com/versity/versitygw/backend/posix.(*Posix).ListMultipartUploads(0xc0004300
/Users/ben/repo/versitygw/backend/posix/posix.go:2122 +0xd25
github.com/versity/versitygw/s3api/controllers.S3ApiController.ListActions({{0x183c
...

This change updates the ListMultipartUploads implementation to properly advance
past the (KeyMarker, UploadIDMarker) tuple when paginating, ensuring that each
response starts after the marker and does not include duplicate uploads.
---
 backend/posix/posix.go | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/backend/posix/posix.go b/backend/posix/posix.go
index bb99ebea..a99b7aa4 100644
--- a/backend/posix/posix.go
+++ b/backend/posix/posix.go
@@ -2117,28 +2117,33 @@ func (p *Posix) ListMultipartUploads(_ context.Context, mpu *s3.ListMultipartUpl
 		return uploads[i].Key < uploads[j].Key
 	})
 
-	for i := keyMarkerInd + 1; i < len(uploads); i++ {
-		if maxUploads == 0 {
-			break
+	start := 0
+	if keyMarker != "" {
+		for i, up := range uploads {
+			if up.Key == keyMarker && (uploadIDMarker == "" ||
+				up.UploadID == uploadIDMarker) {
+				// Start after the marker
+				start = i + 1
+				break
+			}
 		}
-		if keyMarker != "" && uploadIDMarker != "" && uploads[i].UploadID < uploadIDMarker {
-			continue
-		}
-		if i != len(uploads)-1 && len(resultUpds) == maxUploads {
+	}
+
+	for i := start; i < len(uploads); i++ {
+		if len(resultUpds) == maxUploads {
 			return s3response.ListMultipartUploadsResult{
 				Bucket:             bucket,
 				Delimiter:          delimiter,
 				KeyMarker:          keyMarker,
 				MaxUploads:         maxUploads,
-				NextKeyMarker:      resultUpds[i-1].Key,
-				NextUploadIDMarker: resultUpds[i-1].UploadID,
+				NextKeyMarker:      resultUpds[len(resultUpds)-1].Key,
+				NextUploadIDMarker: resultUpds[len(resultUpds)-1].UploadID,
 				IsTruncated:        true,
 				Prefix:             prefix,
 				UploadIDMarker:     uploadIDMarker,
 				Uploads:            resultUpds,
 			}, nil
 		}
-
 		resultUpds = append(resultUpds, uploads[i])
 	}