| Message ID | 20190424110221.17435-7-ming.lei@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | blk-mq: fix races related with freeing queue | expand |
On 4/24/19 1:02 PM, Ming Lei wrote: > In normal queue cleanup path, hctx is released after request queue > is freed, see blk_mq_release(). > > However, in __blk_mq_update_nr_hw_queues(), hctx may be freed because > of hw queues shrinking. This way is easy to cause use-after-free, > because: one implicit rule is that it is safe to call almost all block > layer APIs if the request queue is alive; and one hctx may be retrieved > by one API, then the hctx can be freed by blk_mq_update_nr_hw_queues(); > finally use-after-free is triggered. > > Fixes this issue by always freeing hctx after releasing request queue. > If some hctxs are removed in blk_mq_update_nr_hw_queues(), introduce > a per-queue list to hold them, then try to resuse these hctxs if numa > node is matched. > > Cc: Dongli Zhang <dongli.zhang@oracle.com> > Cc: James Smart <james.smart@broadcom.com> > Cc: Bart Van Assche <bart.vanassche@wdc.com> > Cc: linux-scsi@vger.kernel.org, > Cc: Martin K . Petersen <martin.petersen@oracle.com>, > Cc: Christoph Hellwig <hch@lst.de>, > Cc: James E . J . Bottomley <jejb@linux.vnet.ibm.com>, > Tested-by: James Smart <james.smart@broadcom.com> > Signed-off-by: Ming Lei <ming.lei@redhat.com> > --- > block/blk-mq.c | 46 +++++++++++++++++++++++++++++++++------------- > include/linux/blk-mq.h | 2 ++ > include/linux/blkdev.h | 7 +++++++ > 3 files changed, 42 insertions(+), 13 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 1eceeb26ae7d..b9d711d12cae 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -2274,6 +2274,10 @@ static void blk_mq_exit_hctx(struct request_queue *q, > set->ops->exit_hctx(hctx, hctx_idx); > > blk_mq_remove_cpuhp(hctx); > + > + spin_lock(&q->unused_hctx_lock); > + list_add(&hctx->hctx_list, &q->unused_hctx_list); > + spin_unlock(&q->unused_hctx_lock); > } > > static void blk_mq_exit_hw_queues(struct request_queue *q, > @@ -2362,6 +2366,8 @@ blk_mq_alloc_hctx(struct request_queue *q, > hctx->queue = q; > hctx->flags = set->flags & ~BLK_MQ_F_TAG_SHARED; > > + INIT_LIST_HEAD(&hctx->hctx_list); > + > /* > * Allocate space for all possible cpus to avoid allocation at > * runtime > @@ -2675,15 +2681,17 @@ static int blk_mq_alloc_ctxs(struct request_queue *q) > */ > void blk_mq_release(struct request_queue *q) > { > - struct blk_mq_hw_ctx *hctx; > - unsigned int i; > + struct blk_mq_hw_ctx *hctx, *next; > + int i; > > cancel_delayed_work_sync(&q->requeue_work); > > - /* hctx kobj stays in hctx */ > - queue_for_each_hw_ctx(q, hctx, i) { > - if (!hctx) > - continue; > + queue_for_each_hw_ctx(q, hctx, i) > + WARN_ON_ONCE(hctx && list_empty(&hctx->hctx_list)); > + > + /* all hctx are in .unused_hctx_list now */ > + list_for_each_entry_safe(hctx, next, &q->unused_hctx_list, hctx_list) { > + list_del_init(&hctx->hctx_list); > kobject_put(&hctx->kobj); > } > I would consider it a bug if the hctx is still assigned to ->queue_hw_ctx at this point. But that's a minor issue. Reviewed-by: Hannes Reinecke <hare@suse.com> Cheers, Hannes
diff --git a/block/blk-mq.c b/block/blk-mq.c index 1eceeb26ae7d..b9d711d12cae 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2274,6 +2274,10 @@ static void blk_mq_exit_hctx(struct request_queue *q, set->ops->exit_hctx(hctx, hctx_idx); blk_mq_remove_cpuhp(hctx); + + spin_lock(&q->unused_hctx_lock); + list_add(&hctx->hctx_list, &q->unused_hctx_list); + spin_unlock(&q->unused_hctx_lock); } static void blk_mq_exit_hw_queues(struct request_queue *q, @@ -2362,6 +2366,8 @@ blk_mq_alloc_hctx(struct request_queue *q, hctx->queue = q; hctx->flags = set->flags & ~BLK_MQ_F_TAG_SHARED; + INIT_LIST_HEAD(&hctx->hctx_list); + /* * Allocate space for all possible cpus to avoid allocation at * runtime @@ -2675,15 +2681,17 @@ static int blk_mq_alloc_ctxs(struct request_queue *q) */ void blk_mq_release(struct request_queue *q) { - struct blk_mq_hw_ctx *hctx; - unsigned int i; + struct blk_mq_hw_ctx *hctx, *next; + int i; cancel_delayed_work_sync(&q->requeue_work); - /* hctx kobj stays in hctx */ - queue_for_each_hw_ctx(q, hctx, i) { - if (!hctx) - continue; + queue_for_each_hw_ctx(q, hctx, i) + WARN_ON_ONCE(hctx && list_empty(&hctx->hctx_list)); + + /* all hctx are in .unused_hctx_list now */ + list_for_each_entry_safe(hctx, next, &q->unused_hctx_list, hctx_list) { + list_del_init(&hctx->hctx_list); kobject_put(&hctx->kobj); } @@ -2750,9 +2758,22 @@ static struct blk_mq_hw_ctx *blk_mq_alloc_and_init_hctx( struct blk_mq_tag_set *set, struct request_queue *q, int hctx_idx, int node) { - struct blk_mq_hw_ctx *hctx; + struct blk_mq_hw_ctx *hctx = NULL, *tmp; - hctx = blk_mq_alloc_hctx(q, set, hctx_idx, node); + /* reuse dead hctx first */ + spin_lock(&q->unused_hctx_lock); + list_for_each_entry(tmp, &q->unused_hctx_list, hctx_list) { + if (tmp->numa_node == node) { + hctx = tmp; + break; + } + } + if (hctx) + list_del_init(&hctx->hctx_list); + spin_unlock(&q->unused_hctx_lock); + + if (!hctx) + hctx = blk_mq_alloc_hctx(q, set, hctx_idx, node); if (!hctx) goto fail; @@ -2790,10 +2811,8 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, hctx = blk_mq_alloc_and_init_hctx(set, q, i, node); if (hctx) { - if (hctxs[i]) { + if (hctxs[i]) blk_mq_exit_hctx(q, set, hctxs[i], i); - kobject_put(&hctxs[i]->kobj); - } hctxs[i] = hctx; } else { if (hctxs[i]) @@ -2824,9 +2843,7 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, if (hctx->tags) blk_mq_free_map_and_requests(set, j); blk_mq_exit_hctx(q, set, hctx, j); - kobject_put(&hctx->kobj); hctxs[j] = NULL; - } } mutex_unlock(&q->sysfs_lock); @@ -2869,6 +2886,9 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, if (!q->queue_hw_ctx) goto err_sys_init; + INIT_LIST_HEAD(&q->unused_hctx_list); + spin_lock_init(&q->unused_hctx_lock); + blk_mq_realloc_hw_ctxs(set, q); if (!q->nr_hw_queues) goto err_hctxs; diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index db29928de467..15d1aa53d96c 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -70,6 +70,8 @@ struct blk_mq_hw_ctx { struct dentry *sched_debugfs_dir; #endif + struct list_head hctx_list; + /* Must be the last member - see also blk_mq_hw_ctx_size(). */ struct srcu_struct srcu[0]; }; diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 99aa98f60b9e..d7bad4ae8bc8 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -535,6 +535,13 @@ struct request_queue { struct mutex sysfs_lock; + /* + * for reusing dead hctx instance in case of updating + * nr_hw_queues + */ + struct list_head unused_hctx_list; + spinlock_t unused_hctx_lock; + atomic_t mq_freeze_depth; #if defined(CONFIG_BLK_DEV_BSG)