mon/MDSMonitor: avoid crash when decoding old FSMap epochs

Fixes: https://tracker.ceph.com/issues/52820 Signed-off-by: Patrick Donnelly <[email protected]>
mitsu-ko · Oct 12, 2021 · 631360a · 631360a
1 parent 79a5ded
commit 631360a
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Showing 2 changed files with 7 additions and 1 deletion.
diff --git a/src/mds/FSMap.cc b/src/mds/FSMap.cc
@@ -651,6 +651,7 @@ 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
@@ -2335,7 +2335,12 @@ 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;