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Bug #47015

mds: decoding of enum types on big-endian systems broken

Added by Ulrich Weigand 5 months ago. Updated 4 months ago.

Status:
Resolved
Priority:
Normal
Category:
-
Target version:
% Done:

0%

Source:
Community (dev)
Tags:
Backport:
octopus,nautilus
Regression:
No
Severity:
3 - minor
Reviewed:
Affected Versions:
ceph-qa-suite:
Component(FS):
MDS
Labels (FS):
Pull request ID:
Crash signature:

Description

When a struct member that has enum type needs to be encoded or
decoded, we need to use an explicit integer type, since there
are no encode routines for the enum type. (This is probably
to avoid introducing dependencies on implementation-defined
choices by the compiler to use a particular underlying type.)

This leads to code sequences along the lines of:
encode((int32_t)state, bl);
and
decode((int32_t&)(state), bl);

The encode line is actually fine, but the decode line is
incorrect on big-endian systems if the underlying type of
the enum differs from the explicitly chosen integer type.

This is because this performs in effect a pointer cast,
and will write the decoded int32_t value into the memory
backing the "state" member variable. If the sizes differ,
the value is written into the wrong bytes of "state" on
big-endian systems.

This bug showed up initially as invalid health-status values
causing Ceph daemon aborts on s390x. Code review uncovered
a number of other instances of the same enum decode pattern.


Related issues

Copied to CephFS - Backport #47080: octopus: mds: decoding of enum types on big-endian systems broken Resolved
Copied to CephFS - Backport #47081: nautilus: mds: decoding of enum types on big-endian systems broken Resolved

History

#1 Updated by Patrick Donnelly 5 months ago

  • Status changed from New to Fix Under Review
  • Assignee set to Ulrich Weigand
  • Target version set to v16.0.0
  • Source set to Community (dev)
  • Backport set to octopus,nautilus

#2 Updated by Patrick Donnelly 5 months ago

  • Project changed from Ceph to CephFS
  • Subject changed from Decoding of enum types on big-endian systems broken to mds: decoding of enum types on big-endian systems broken
  • Component(FS) MDS added

#3 Updated by Patrick Donnelly 5 months ago

  • Status changed from Fix Under Review to Pending Backport

#4 Updated by Nathan Cutler 5 months ago

  • Copied to Backport #47080: octopus: mds: decoding of enum types on big-endian systems broken added

#5 Updated by Nathan Cutler 5 months ago

  • Copied to Backport #47081: nautilus: mds: decoding of enum types on big-endian systems broken added

#6 Updated by Ulrich Weigand 5 months ago

Thanks for creating the backport requests!

Would it make sense to also include this commit for backporting:
https://github.com/ceph/ceph/pull/35920

It is similarly a bug with decoding certain messages on big-endian systems. Unfortunately I didn't think to open a issue tracker back then ...

#7 Updated by Patrick Donnelly 5 months ago

Ulrich Weigand wrote:

Thanks for creating the backport requests!

Would it make sense to also include this commit for backporting:
https://github.com/ceph/ceph/pull/35920

It is similarly a bug with decoding certain messages on big-endian systems. Unfortunately I didn't think to open a issue tracker back then ...

Yes, I've made a note in the backport trackers.

#8 Updated by Nathan Cutler 4 months ago

  • Status changed from Pending Backport to Resolved

While running with --resolve-parent, the script "backport-create-issue" noticed that all backports of this issue are in status "Resolved" or "Rejected".

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