Commit 34c3a47d authored by Daniel Jordan's avatar Daniel Jordan Committed by Herbert Xu
Browse files

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: default avatar <syzbot+bc05445bc14148d51915@syzkaller.appspotmail.com>
Fixes: 4611ce22 ("padata: allocate work structures for parallel jobs from a pool")
Signed-off-by: default avatarDaniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 1aa33fc8

kernel/padata.c

+5 −3
Original line number Diff line number Diff line
@@ -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;