[Bug 2146842] Re: tcmalloc RSEQ ABI violation causes crashes on linux kernel 6.19+

[Christian Ehrhardt]

We pondered if this warrants a release notes entry or not, but there is
nothing in the Archive that is affected nor something in the archive
that we'd change to fix it. Hence it feels wrong to do that.

What bug would we refer to? Just the upstream case - but then I'm sure a
jump of kernel versions needs adaptations in hundreds of more places and
we do not mention them either.

This place and bug report here is appropriate - search engines and user
can find it, it summarized the state and it explains why we are not
affected in any direct way. It links to the upstream case in tcmalloc
for reference and that contains how this will evolve.

TBH the fight between kernel and tcmalloc who broke whom or who relied
on behavior not meant to rely on is not our fight. I'm sure they will
find a compromise that works and then release either a tcmalloc change
(and since the tcmalloc in Ubuntu does not have the affected code that
is a no-op) or a kernel change (in which case the kernel will pick it
up). For the potential of the latter I'll add a kernel bug task but mark
it incomplete for now (as there is nothing to act on, but good to have
them aware).


** Also affects: linux (Ubuntu)
   Importance: Undecided
       Status: New

** Changed in: linux (Ubuntu)
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/2146842

Title:
  tcmalloc RSEQ ABI violation causes crashes on linux kernel 6.19+

Status in Google Perftools Packaging:
  New
Status in google-perftools package in Ubuntu:
  Invalid
Status in linux package in Ubuntu:
  Incomplete

Bug description:
  With the 6.19 release of the Linux kernel, upstream MongoDB now
  experiences crashes after ~30 seconds due to an RSEQ error from
  tcmalloc. The unit test
  //tcmalloc/testing:background_test_no_glibc_rseq notably also fails on
  6.19 and 7.0, and may be due to the following commit -
  https://lore.kernel.org/all/20251027084307.578058898@linutronix.de/

  While mongodb is not supported in the Ubuntu archive, there are other
  packages using tcmalloc such as mysql-8.4 which may be affected.

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