From: Yu Kuai yukuai3@huawei.com
mainline inclusion from mainline-v6.2-rc5 commit 216f764716f34fe68cedc7296ae2043a7727e640 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I6DYRK CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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The updating of 'bfqg->ref' should be protected by 'bfqd->lock', however, during code review, we found that bfq_pd_free() update 'bfqg->ref' without holding the lock, which is problematic:
1) bfq_pd_free() triggered by removing cgroup is called asynchronously; 2) bfqq will grab bfqg reference, and exit bfqq will drop the reference, which can concurrent with 1).
Unfortunately, 'bfqd->lock' can't be held here because 'bfqd' might already be freed in bfq_pd_free(). Fix the problem by using atomic refcount apis.
Signed-off-by: Yu Kuai yukuai3@huawei.com Reviewed-by: Jan Kara jack@suse.cz Link: https://lore.kernel.org/r/20230103084755.1256479-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe axboe@kernel.dk Reviewed-by: Hou Tao houtao1@huawei.com Signed-off-by: Jialin Zhang zhangjialin11@huawei.com --- block/bfq-cgroup.c | 8 +++----- block/bfq-iosched.h | 2 +- 2 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index a285711f1b48..06c82d689ef0 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -321,14 +321,12 @@ struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
static void bfqg_get(struct bfq_group *bfqg) { - bfqg->ref++; + refcount_inc(&bfqg->ref); }
static void bfqg_put(struct bfq_group *bfqg) { - bfqg->ref--; - - if (bfqg->ref == 0) + if (refcount_dec_and_test(&bfqg->ref)) kfree(bfqg); }
@@ -535,7 +533,7 @@ static struct blkg_policy_data *bfq_pd_alloc(gfp_t gfp, struct request_queue *q, }
/* see comments in bfq_bic_update_cgroup for why refcounting */ - bfqg_get(bfqg); + refcount_set(&bfqg->ref, 1); return &bfqg->pd; }
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index 2a4a6f44efff..f6d9adfd1fc6 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -900,7 +900,7 @@ struct bfq_group { char blkg_path[128];
/* reference counter (see comments in bfq_bic_update_cgroup) */ - int ref; + refcount_t ref; /* Is bfq_group still online? */ bool online;