In the Linux kernel, the following vulnerability has been resolved:

padata: Always leave BHs disabled when running ->parallel()

A deadlock can happen when an overloaded system runs ->parallel() in the
context of the current task:

padata_do_parallel
  ->parallel()
    pcrypt_aead_enc/dec
      padata_do_serial
        spin_lock(&reorder->lock) // BHs still enabled
          <interrupt>
            ...
              __do_softirq
                ...
                  padata_do_serial
                    spin_lock(&reorder->lock)

It's a bug for BHs to be on in _do_serial as Steffen points out, so
ensure they're off in the "current task" case like they are in
padata_parallel_worker to avoid this situation.

References

• https://nvd.nist.gov/vuln/detail/CVE-2022-50382
• https://git.kernel.org/stable/c/17afa98bccec4f52203508b3f49b5f948c6fd6ac
• https://git.kernel.org/stable/c/34c3a47d20ae55b3600fed733bf96eafe9c500d5
• https://git.kernel.org/stable/c/6cfa9e60c0f88fdec6368e081ab968411cc706b1
• https://git.kernel.org/stable/c/7337adb20fcc0aebb50eaff2bc5a8dd9a7c6743d
• https://git.kernel.org/stable/c/8e0681dd4eee029eb1d533d06993f7cb091efb73