From: Daniel Jordan daniel.m.jordan@oracle.com
[ Upstream commit 34c3a47d20ae55b3600fed733bf96eafe9c500d5 ]
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: 4611ce224688 ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/padata.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/kernel/padata.c b/kernel/padata.c index d4d3ba6e1728..4d31a69a9b38 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -220,14 +220,16 @@ 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;