fix(pools): keep rejected names out of a single-pool bulk delete

DeleteObjects checks every name with checkDelObjArgs, but a single pool
still sent all entries to the drives and cleared the error of an entry
that a drive reported as found. Local drives join the name to the bucket
directory, so a name with a ".." segment reached another bucket or the
meta bucket. An S3 DeleteObjects caller allowed to delete in one bucket
could remove a version elsewhere, including one under Object Lock
retention, and from a versioned bucket could write a delete marker on an
object of another bucket or on stored bucket metadata. The bulk lock was
taken on the normalized name as well, that is on the other object.

Entries that fail the check now keep their error, and the rest of the
request runs as a request of its own, before any lock or lookup. A
request whose names are all valid does not enter the new code. More than
one pool already skipped such entries.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>
Signed-off-by: Feng Ruohang <rh@vonng.com>

cmd/erasure-server-pool.go

@@ -26,6 +26,7 @@ import (
 	"math/rand"
 	"net/http"
 	"path"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -1543,6 +1544,27 @@ func (z *erasureServerPools) DeleteObjects(ctx context.Context, bucket string, o
 		objSets.Add(objects[i].ObjectName)
 	}
 
+	// A name that fails the check keeps its error and goes no further. Joined
+	// to the bucket it can name a path in another bucket or in the meta
+	// bucket, so it is not locked, looked up or sent to a drive. The other
+	// names are deleted as a request of their own: everything below sees only
+	// names that passed.
+	if slices.ContainsFunc(derrs, func(err error) bool { return err != nil }) {
+		valid, at := make([]ObjectToDelete, 0, len(objects)), make([]int, 0, len(objects))
+		for i, obj := range objects {
+			if derrs[i] == nil {
+				valid, at = append(valid, obj), append(at, i)
+			}
+		}
+		if len(valid) > 0 {
+			deleted, errs := z.DeleteObjects(ctx, bucket, valid, opts)
+			for j, i := range at {
+				dobjects[i], derrs[i] = deleted[j], errs[j]
+			}
+		}
+		return dobjects, derrs
+	}
+
 	// A single pool locks each name in the set its writers lock it in, one
 	// set at a time. A single node keeps one lock table for all sets, so it
 	// keeps the one bulk lock below: its local lock takes the names one by