5.15-stable review patch. If anyone has any objections, please let me know.
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From: Yu Kuai yukuai3@huawei.com
commit dfd6200a095440b663099d8d42f1efb0175a1ce3 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- block/blk-cgroup.c | 24 +++++++++++++++++------- include/linux/blk-cgroup.h | 1 + 2 files changed, 18 insertions(+), 7 deletions(-)
--- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -192,6 +192,7 @@ static struct blkcg_gq *blkg_alloc(struc blkg->pd[i] = pd; pd->blkg = blkg; pd->plid = i; + pd->online = false; }
return blkg; @@ -289,8 +290,11 @@ static struct blkcg_gq *blkg_create(stru 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; @@ -390,8 +394,11 @@ static void blkg_destroy(struct blkcg_gq 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; @@ -1367,6 +1374,7 @@ retry: blkg->pd[pol->plid] = pd; pd->blkg = blkg; pd->plid = pol->plid; + pd->online = false; }
/* all allocated, init in the same order */ @@ -1374,9 +1382,11 @@ retry: 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; @@ -1438,7 +1448,7 @@ void blkcg_deactivate_policy(struct requ
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; --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -92,6 +92,7 @@ struct blkg_policy_data { /* the blkg and policy id this per-policy data belongs to */ struct blkcg_gq *blkg; int plid; + bool online; };
/*