| Message ID | 20221117012802.62504-1-daniel.m.jordan@oracle.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Herbert Xu |
| Headers | show |
| Series | padata: Always leave BHs disabled when running ->parallel() | expand |
On Wed, Nov 16, 2022 at 08:28:02PM -0500, Daniel Jordan wrote: > 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> > --- > > About the potential deadlock in padata_find_next(), I think this fix > covers us there since that function is only called from > padata_do_serial(), where BHs should now always be off, or > invoke_padata_reorder(), where BHs are off as well. The _bh spinlock > variants in padata_reorder() seem redundant. > > kernel/padata.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) Patch applied. Thanks.
diff --git a/kernel/padata.c b/kernel/padata.c index e5819bb8bd1d..97f51e0c1776 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;
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> --- About the potential deadlock in padata_find_next(), I think this fix covers us there since that function is only called from padata_do_serial(), where BHs should now always be off, or invoke_padata_reorder(), where BHs are off as well. The _bh spinlock variants in padata_reorder() seem redundant. kernel/padata.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)