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blk-cgroup: cleanup and bugfixs in blk-cgroup #459

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blk-cgroup: cleanup and bugfixs in blk-cgroup #459

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6bdfdc6
blk-cgroup: factor policy pd teardown loop into helper
Jan 8, 2026
4cdbcc5
blk-cgroup: fix uaf in blkcg_activate_policy() racing with blkg_free_…
Jan 8, 2026
e637731
blk-cgroup: skip dying blkg in blkcg_activate_policy()
Jan 8, 2026
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63 changes: 31 additions & 32 deletions block/blk-cgroup.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1559,6 +1559,31 @@ struct cgroup_subsys io_cgrp_subsys = {
};
EXPORT_SYMBOL_GPL(io_cgrp_subsys);

/*
* Tear down per-blkg policy data for @pol on @q.
*/
static void blkcg_policy_teardown_pds(struct request_queue *q,
const struct blkcg_policy *pol)
{
struct blkcg_gq *blkg;

list_for_each_entry(blkg, &q->blkg_list, q_node) {
struct blkcg *blkcg = blkg->blkcg;
struct blkg_policy_data *pd;

spin_lock(&blkcg->lock);
pd = blkg->pd[pol->plid];
if (pd) {
if (pd->online && pol->pd_offline_fn)
pol->pd_offline_fn(pd);
pd->online = false;
pol->pd_free_fn(pd);
blkg->pd[pol->plid] = NULL;
}
spin_unlock(&blkcg->lock);
}
}

/**
* blkcg_activate_policy - activate a blkcg policy on a gendisk
* @disk: gendisk of interest
Expand Down Expand Up @@ -1620,9 +1645,10 @@ int blkcg_activate_policy(struct gendisk *disk, const struct blkcg_policy *pol)
* GFP_NOWAIT failed. Free the existing one and
* prealloc for @blkg w/ GFP_KERNEL.
*/
if (!blkg_tryget(blkg))
continue;
if (pinned_blkg)
blkg_put(pinned_blkg);
blkg_get(blkg);
pinned_blkg = blkg;

spin_unlock_irq(&q->queue_lock);
Expand Down Expand Up @@ -1668,23 +1694,11 @@ int blkcg_activate_policy(struct gendisk *disk, const struct blkcg_policy *pol)

enomem:
/* alloc failed, take down everything */
mutex_lock(&q->blkcg_mutex);
spin_lock_irq(&q->queue_lock);
list_for_each_entry(blkg, &q->blkg_list, q_node) {
struct blkcg *blkcg = blkg->blkcg;
struct blkg_policy_data *pd;

spin_lock(&blkcg->lock);
pd = blkg->pd[pol->plid];
if (pd) {
if (pd->online && pol->pd_offline_fn)
pol->pd_offline_fn(pd);
pd->online = false;
pol->pd_free_fn(pd);
blkg->pd[pol->plid] = NULL;
}
spin_unlock(&blkcg->lock);
}
blkcg_policy_teardown_pds(q, pol);
spin_unlock_irq(&q->queue_lock);
mutex_unlock(&q->blkcg_mutex);
ret = -ENOMEM;
goto out;
}
Expand All @@ -1702,7 +1716,6 @@ void blkcg_deactivate_policy(struct gendisk *disk,
const struct blkcg_policy *pol)
{
struct request_queue *q = disk->queue;
struct blkcg_gq *blkg;
unsigned int memflags;

if (!blkcg_policy_enabled(q, pol))
Expand All @@ -1713,22 +1726,8 @@ void blkcg_deactivate_policy(struct gendisk *disk,

mutex_lock(&q->blkcg_mutex);
spin_lock_irq(&q->queue_lock);

__clear_bit(pol->plid, q->blkcg_pols);

list_for_each_entry(blkg, &q->blkg_list, q_node) {
struct blkcg *blkcg = blkg->blkcg;

spin_lock(&blkcg->lock);
if (blkg->pd[pol->plid]) {
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;
}
spin_unlock(&blkcg->lock);
}

blkcg_policy_teardown_pds(q, pol);
spin_unlock_irq(&q->queue_lock);
mutex_unlock(&q->blkcg_mutex);

Expand Down