From: Yu Kuai yukuai3@huawei.com

[ Upstream commit dfd6200a095440b663099d8d42f1efb0175a1ce3 ]

A new field 'online' is added to blkg_policy_data to fix following 2 problem:

1) In blkcg_activate_policy(), if pd_alloc_fn() with 'GFP_NOWAIT' failed, 'queue_lock' will be dropped and pd_alloc_fn() will try again without 'GFP_NOWAIT'. In the meantime, remove cgroup can race with it, and pd_offline_fn() will be called without pd_init_fn() and pd_online_fn(). This way null-ptr-deference can be triggered.

2) In order to synchronize pd_free_fn() from blkg_free_workfn() and blkcg_deactivate_policy(), 'list_del_init(&blkg->q_node)' will be delayed to blkg_free_workfn(), hence pd_offline_fn() can be called first in blkg_destroy(), and then blkcg_deactivate_policy() will call it again, we must prevent it.

The new field 'online' will be set after pd_online_fn() and will be cleared after pd_offline_fn(), in the meantime pd_offline_fn() will only be called if 'online' is set.

Signed-off-by: Yu Kuai yukuai3@huawei.com Acked-by: Tejun Heo tj@kernel.org Reviewed-by: Christoph Hellwig hch@lst.de Link: https://lore.kernel.org/r/20230119110350.2287325-3-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Bin Lan bin.lan.cn@windriver.com Signed-off-by: He Zhe zhe.he@windriver.com --- Build test passed. --- block/blk-cgroup.c | 24 +++++++++++++++++------- block/blk-cgroup.h | 1 + 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index cced5a2d5fb6..ef596fc10465 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -255,6 +255,7 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct gendisk *disk, blkg->pd[i] = pd; pd->blkg = blkg; pd->plid = i; + pd->online = false; }

return blkg; @@ -326,8 +327,11 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, struct gendisk *disk, for (i = 0; i < BLKCG_MAX_POLS; i++) { struct blkcg_policy *pol = blkcg_policy[i];

- if (blkg->pd[i] && pol->pd_online_fn) - pol->pd_online_fn(blkg->pd[i]); + if (blkg->pd[i]) { + if (pol->pd_online_fn) + pol->pd_online_fn(blkg->pd[i]); + blkg->pd[i]->online = true; + } } } blkg->online = true; @@ -432,8 +436,11 @@ static void blkg_destroy(struct blkcg_gq *blkg) for (i = 0; i < BLKCG_MAX_POLS; i++) { struct blkcg_policy *pol = blkcg_policy[i];

- if (blkg->pd[i] && pol->pd_offline_fn) - pol->pd_offline_fn(blkg->pd[i]); + if (blkg->pd[i] && blkg->pd[i]->online) { + if (pol->pd_offline_fn) + pol->pd_offline_fn(blkg->pd[i]); + blkg->pd[i]->online = false; + } }

blkg->online = false; @@ -1422,6 +1429,7 @@ int blkcg_activate_policy(struct request_queue *q, blkg->pd[pol->plid] = pd; pd->blkg = blkg; pd->plid = pol->plid; + pd->online = false; }

/* all allocated, init in the same order */ @@ -1429,9 +1437,11 @@ int blkcg_activate_policy(struct request_queue *q, list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) pol->pd_init_fn(blkg->pd[pol->plid]);

- if (pol->pd_online_fn) - list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) + list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) { + if (pol->pd_online_fn) pol->pd_online_fn(blkg->pd[pol->plid]); + blkg->pd[pol->plid]->online = true; + }

__set_bit(pol->plid, q->blkcg_pols); ret = 0; @@ -1493,7 +1503,7 @@ void blkcg_deactivate_policy(struct request_queue *q,

spin_lock(&blkcg->lock); if (blkg->pd[pol->plid]) { - if (pol->pd_offline_fn) + if (blkg->pd[pol->plid]->online && pol->pd_offline_fn) pol->pd_offline_fn(blkg->pd[pol->plid]); pol->pd_free_fn(blkg->pd[pol->plid]); blkg->pd[pol->plid] = NULL; diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h index aa2b286bc825..59815b269a20 100644 --- a/block/blk-cgroup.h +++ b/block/blk-cgroup.h @@ -125,6 +125,7 @@ struct blkg_policy_data { /* the blkg and policy id this per-policy data belongs to */ struct blkcg_gq *blkg; int plid; + bool online; };

/*