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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.

Reported-by: syzbot+bc05445bc14148d51915@syzkaller.appspotmail.com
Fixes: 4611ce2246 ("padata: allocate work structures for parallel jobs from a pool")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Daniel Jordan 2022-11-16 20:28:02 -05:00 committed by Herbert Xu
parent 1aa33fc8d4
commit 34c3a47d20
1 changed files with 5 additions and 3 deletions
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8
kernel/padata.c
View File

@ -207,14 +207,16 @@ int padata_do_parallel(struct padata_shell *ps,
pw = padata_work_alloc();
spin_unlock(&padata_works_lock);
if (!pw) {
/* Maximum works limit exceeded, run in the current task. */
padata->parallel(padata);
}
rcu_read_unlock_bh();
if (pw) {
padata_work_init(pw, padata_parallel_worker, padata, 0);
queue_work(pinst->parallel_wq, &pw->pw_work);
} else {
/* Maximum works limit exceeded, run in the current task. */
padata->parallel(padata);
}
return 0;