[PATCH 6.6 035/122] block: fix q->blkg_list corruption during disk rebind

Greg Kroah-Hartman
2024-04-15T14:33:57Z

From: Ming Lei <ming.lei@redhat.com>

[ Upstream commit 8b8ace080319a866f5dfe9da8e665ae51d971c54 ]

Multiple gendisk instances can allocated/added for single request queue
in case of disk rebind. blkg may still stay in q->blkg_list when calling
blkcg_init_disk() for rebind, then q->blkg_list becomes corrupted.

Fix the list corruption issue by:

- add blkg_init_queue() to initialize q->blkg_list & q->blkcg_mutex only
- move calling blkg_init_queue() into blk_alloc_queue()

The list corruption should be started since commit f1c006f1c685 ("blk-cgroup:
synchronize pd_free_fn() from blkg_free_workfn() and blkcg_deactivate_policy()")
which delays removing blkg from q->blkg_list into blkg_free_workfn().

Fixes: f1c006f1c685 ("blk-cgroup: synchronize pd_free_fn() from blkg_free_workfn() and blkcg_deactivate_policy()")
Fixes: 1059699f87eb ("block: move blkcg initialization/destroy into disk allocation/release handler")
Cc: Yu Kuai <yukuai3@huawei.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240407125910.4053377-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/blk-cgroup.c | 9 ++++++---
block/blk-cgroup.h | 2 ++
block/blk-core.c | 2 ++
3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 4b48c2c440981..4c49a70b46bd1 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1409,6 +1409,12 @@ static int blkcg_css_online(struct cgroup_subsys_state *css)
return 0;
}

+void blkg_init_queue(struct request_queue *q)
+{
+ INIT_LIST_HEAD(&q->blkg_list);
+ mutex_init(&q->blkcg_mutex);
+}
+
int blkcg_init_disk(struct gendisk *disk)
{
struct request_queue *q = disk->queue;
@@ -1416,9 +1422,6 @@ int blkcg_init_disk(struct gendisk *disk)
bool preloaded;
int ret;

- INIT_LIST_HEAD(&q->blkg_list);
- mutex_init(&q->blkcg_mutex);
-
new_blkg = blkg_alloc(&blkcg_root, disk, GFP_KERNEL);
if (!new_blkg)
return -ENOMEM;
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index b927a4a0ad030..5b0bdc268ade9 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -188,6 +188,7 @@ struct blkcg_policy {
extern struct blkcg blkcg_root;
extern bool blkcg_debug_stats;

+void blkg_init_queue(struct request_queue *q);
int blkcg_init_disk(struct gendisk *disk);
void blkcg_exit_disk(struct gendisk *disk);

@@ -481,6 +482,7 @@ struct blkcg {
};

static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
+static inline void blkg_init_queue(struct request_queue *q) { }
static inline int blkcg_init_disk(struct gendisk *disk) { return 0; }
static inline void blkcg_exit_disk(struct gendisk *disk) { }
static inline int blkcg_policy_register(struct blkcg_policy *pol) { return 0; }
diff --git a/block/blk-core.c b/block/blk-core.c
index 2eca76ccf4ee0..a3726d8cf8738 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -430,6 +430,8 @@ struct request_queue *blk_alloc_queue(int node_id)
init_waitqueue_head(&q->mq_freeze_wq);
mutex_init(&q->mq_freeze_lock);

+ blkg_init_queue(q);
+
/*
* Init percpu_ref in atomic mode so that it's faster to shutdown.
* See blk_register_queue() for details.
--
2.43.0