From 17afa98bccec4f52203508b3f49b5f948c6fd6ac Mon Sep 17 00:00:00 2001 From: Daniel Jordan Date: Wed, 16 Nov 2022 20:28:02 -0500 Subject: [PATCH] padata: Always leave BHs disabled when running ->parallel() [ 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 ... __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 Acked-by: Steffen Klassert Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin --- kernel/padata.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/padata.c b/kernel/padata.c index 18d3a5c..9395b77 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -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; -- 2.7.4