From: Patrick Donnelly <pdonnell@redhat.com>
Date: Tue, 12 Oct 2021 18:00:50 +0000 (-0400)
Subject: mon/MDSMonitor: avoid crash when decoding old FSMap epochs
X-Git-Tag: v16.2.7~68^2
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=refs%2Fpull%2F43615%2Fhead;p=ceph.git

mon/MDSMonitor: avoid crash when decoding old FSMap epochs

Fixes: https://tracker.ceph.com/issues/52820
Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit 631360a41ab2ad93445d35a9730200beef2bebab)
---

diff --git a/src/mds/FSMap.cc b/src/mds/FSMap.cc
index 9508e8df2c9e..9be570e537a7 100644
--- a/src/mds/FSMap.cc
+++ b/src/mds/FSMap.cc
@@ -641,6 +641,7 @@ void FSMap::encode(bufferlist& bl, uint64_t features) const
 
 void FSMap::decode(bufferlist::const_iterator& p)
 {
+  struct_version = 0;
   DECODE_START(STRUCT_VERSION, p);
   DECODE_OLDEST(7);
   struct_version = struct_v;
diff --git a/src/mon/MDSMonitor.cc b/src/mon/MDSMonitor.cc
index 419447befa42..ac2bd2d15759 100644
--- a/src/mon/MDSMonitor.cc
+++ b/src/mon/MDSMonitor.cc
@@ -2306,7 +2306,12 @@ void MDSMonitor::tick()
         derr << "could not get version " << v << dendl;
         ceph_abort();
       }
-      fsmap.decode(bl);
+      try {
+        fsmap.decode(bl);
+      } catch (const ceph::buffer::malformed_input& e) {
+        dout(5) << "flushing old fsmap struct because unable to decode FSMap: " << e.what() << dendl;
+      }
+      /* N.B. FSMap::is_struct_old is also true for undecoded (failed to decode) FSMap */
       if (fsmap.is_struct_old()) {
         dout(5) << "fsmap struct is too old; proposing to flush out old versions" << dendl;
         do_propose = true;