From: Yan, Zheng <zyan@redhat.com>
Date: Mon, 11 Nov 2019 15:28:16 +0000 (+0800)
Subject: mds: fix invalid access of mdr->dn[0].back()
X-Git-Tag: v15.1.0~822^2
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=e906001b860b8c1b403ee4acd04818fe8bb8e801;p=ceph.git

mds: fix invalid access of mdr->dn[0].back()

Introduced by commit 79abdcb31af

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Fixes: https://tracker.ceph.com/issues/42746
---

diff --git a/src/mds/MDCache.cc b/src/mds/MDCache.cc
index e7472abdf812..83106de5122c 100644
--- a/src/mds/MDCache.cc
+++ b/src/mds/MDCache.cc
@@ -9365,12 +9365,12 @@ void MDCache::request_forward(MDRequestRef& mdr, mds_rank_t who, int port)
 	  }
 	case CEPH_MDS_OP_LOOKUP:
 	  {
-	    CDentry* dn = mdr->dn[0].back();
-	    if (dn) {
+	    if (mdr->dn[0].size()) {
+	      CDentry* dn = mdr->dn[0].back();
 	      auto it = dn->batch_ops.find(mask);
 	      if (it != dn->batch_ops.end()) {
-                it->second->forward(who);
-                dn->batch_ops.erase(it);
+		it->second->forward(who);
+		dn->batch_ops.erase(it);
 	      }
 	    }
 	    break;