[Bug 2089565] Re: MON and MDS crash upgrading CEPH on ubuntu 24.04 LTS

[Maksym Medvied]

The fix for the bug looks at the byte 4 bytes ahead (if the current
position is 0x3C9, then the code would look at the byte at 0x3CD). In
the squid release the byte most likely would be 0 (it could be non-zero
for 4GiB+ extended attributes, which is highly unlikely). In the squid
git snapshot from 24.04 release it would be the first char of a decimal
representation of a number, which is either "-" (0x2D) or a number (a
value from 0x30 to 0x39). This patch assumes that max_xattr_size is less
than 64GiB and checks the byte against 0x10, and then uses the correct
decoding order for bal_rank_mask and max_xattr_size for each situation.

Reef 18.2.4 has bal_rank_mask and then max_xattr_size in the same order
as they are in the squid release.

Quincy 17.2.7 has neither of the 2 fields.

** Patch added: "src/mds/MDSMap: decode max_xattr_size and bal_rank_mask in the right order"
   https://bugs.launchpad.net/ubuntu/+source/ceph/+bug/2089565/+attachment/5859270/+files/MDSMap-decode-max_xattr_size-and-bal_rank_mask.patch

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Title:
  MON and MDS crash upgrading  CEPH  on ubuntu 24.04 LTS

Status in ceph package in Ubuntu:
  In Progress

Bug description:
  This issue is a continuation of
  https://bugs.launchpad.net/ubuntu/+source/ceph/+bug/2065515

  
  On Ubuntu 24.04 lts we did upgrade Ceph to  19.2.0-0ubuntu0.24.04.1

  Previous release is : 19.2.0~git20240301.4c76c50-0ubuntu6

  whenever  upgrading (tested on 2 different clusters)  the ceph-mon
  ends up crashing repeatedly with the below stack error

  ```
   ceph version 19.2.0 (16063ff2022298c9300e49a547a16ffda59baf13) squid (stable)
   1: /lib/x86_64-linux-gnu/libc.so.6(+0x45320) [0x788409245320]
   2: pthread_kill()
   3: gsignal()
   4: abort()
   5: /lib/x86_64-linux-gnu/libstdc++.so.6(+0xa5ff5) [0x7884096a5ff5]
   6: /lib/x86_64-linux-gnu/libstdc++.so.6(+0xbb0da) [0x7884096bb0da]
   7: (std::unexpected()+0) [0x7884096a5a55]
   8: /lib/x86_64-linux-gnu/libstdc++.so.6(+0xbb391) [0x7884096bb391]
   9: (ceph::buffer::v15_2_0::list::iterator_impl<true>::copy(unsigned int, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&)+0x193) [0x78840a293593]
   10: (MDSMap::decode(ceph::buffer::v15_2_0::list::iterator_impl<true>&)+0xca1) [0x78840a4c3ab1]
   11: (Filesystem::decode(ceph::buffer::v15_2_0::list::iterator_impl<true>&)+0x1c3) [0x78840a4e4303]
   12: (FSMap::decode(ceph::buffer::v15_2_0::list::iterator_impl<true>&)+0x280) [0x78840a4e6ef0]
   13: (MDSMonitor::update_from_paxos(bool*)+0x291) [0x631ac5dea801]
   14: (Monitor::refresh_from_paxos(bool*)+0x124) [0x631ac5b7a164]
   15: (Monitor::preinit()+0x98e) [0x631ac5bb2fbe]
   16: main()
   17: /lib/x86_64-linux-gnu/libc.so.6(+0x2a1ca) [0x78840922a1ca]
   18: __libc_start_main()
   19: _start()
   NOTE: a copy of the executable, or `objdump -rdS <executable>` is needed to interpret this.

  ```

  
  mitigation:
  a rollback to the previous release 19.2.0~git20240301.4c76c50-0ubuntu6 is still possible to restore service

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