[PATCH 6.1 0634/1146] padata: Fix list iterator in padata_do_serial()

Greg Kroah-Hartman
2022-12-28T16:17:19Z

From: Daniel Jordan <daniel.m.jordan@oracle.com>

[ Upstream commit 57ddfecc72a6c9941d159543e1c0c0a74fe9afdd ]

list_for_each_entry_reverse() assumes that the iterated list is nonempty
and that every list_head is embedded in the same type, but its use in
padata_do_serial() breaks both rules.

This doesn't cause any issues now because padata_priv and padata_list
happen to have their list fields at the same offset, but we really
shouldn't be relying on that.

Fixes: bfde23ce200e ("padata: unbind parallel jobs from specific CPUs")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/padata.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/padata.c b/kernel/padata.c
index 97f51e0c1776..de90af5fcbe6 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -390,13 +390,16 @@ void padata_do_serial(struct padata_priv *padata)
int hashed_cpu = padata_cpu_hash(pd, padata->seq_nr);
struct padata_list *reorder = per_cpu_ptr(pd->reorder_list, hashed_cpu);
struct padata_priv *cur;
+ struct list_head *pos;

spin_lock(&reorder->lock);
/* Sort in ascending order of sequence number. */
- list_for_each_entry_reverse(cur, &reorder->list, list)
+ list_for_each_prev(pos, &reorder->list) {
+ cur = list_entry(pos, struct padata_priv, list);
if (cur->seq_nr < padata->seq_nr)
break;
- list_add(&padata->list, &cur->list);
+ }
+ list_add(&padata->list, pos);
spin_unlock(&reorder->lock);

/*
--
2.35.1