From: Yu Kuai <yukuai3@huawei.com> hulk inclusion category: bugfix bugzilla: 186389, https://gitee.com/openeuler/kernel/issues/I4Y43S CVE: NA -------------------------------- blk_mq_realloc_hw_ctxs() will free the 'queue_hw_ctx'(e.g. undate submit_queues through configfs for null_blk), while it might still be used from other context(e.g. switch elevator to none): t1 t2 elevator_switch blk_mq_unquiesce_queue blk_mq_run_hw_queues queue_for_each_hw_ctx // assembly code for hctx = (q)->queue_hw_ctx[i] mov 0x48(%rbp),%rdx -> read old queue_hw_ctx __blk_mq_update_nr_hw_queues blk_mq_realloc_hw_ctxs hctxs = q->queue_hw_ctx q->queue_hw_ctx = new_hctxs kfree(hctxs) movslq %ebx,%rax mov (%rdx,%rax,8),%rdi ->uaf Sicne the queue is freezed in __blk_mq_update_nr_hw_queues(), fix the problem by protecting 'queue_hw_ctx' through rcu where it can be accessed without grabbing 'q_usage_counter'. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Zhang Wensheng <zhangwensheng5@huawei.com> Reviewed-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- block/blk-mq.c | 10 +++++++++- include/linux/blk-mq.h | 13 ++++++++++++- include/linux/blkdev.h | 2 +- 3 files changed, 22 insertions(+), 3 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 9ae1663348ac..cedc355218db 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -3280,7 +3280,15 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, if (hctxs) memcpy(new_hctxs, hctxs, q->nr_hw_queues * sizeof(*hctxs)); - q->queue_hw_ctx = new_hctxs; + + rcu_assign_pointer(q->queue_hw_ctx, new_hctxs); + /* + * Make sure reading the old queue_hw_ctx from other + * context concurrently won't trigger uaf. and when + * it is in start up time, no need to sync rcu. + */ + if (hctxs) + synchronize_rcu(); kfree(hctxs); hctxs = new_hctxs; } diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index b2db9a5c10e8..c9210fb70e4d 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -612,9 +612,20 @@ static inline void *blk_mq_rq_to_pdu(struct request *rq) return rq + 1; } +static inline struct blk_mq_hw_ctx *queue_hctx(struct request_queue *q, int id) +{ + struct blk_mq_hw_ctx *hctx; + + rcu_read_lock(); + hctx = *(rcu_dereference(q->queue_hw_ctx) + id); + rcu_read_unlock(); + + return hctx; +} + #define queue_for_each_hw_ctx(q, hctx, i) \ for ((i) = 0; (i) < (q)->nr_hw_queues && \ - ({ hctx = (q)->queue_hw_ctx[i]; 1; }); (i)++) + ({ hctx = queue_hctx((q), i); 1; }); (i)++) #define hctx_for_each_ctx(hctx, ctx, i) \ for ((i) = 0; (i) < (hctx)->nr_ctx && \ diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 433485f8b1cc..23dfe7608e79 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -421,7 +421,7 @@ struct request_queue { unsigned int queue_depth; /* hw dispatch queues */ - struct blk_mq_hw_ctx **queue_hw_ctx; + struct blk_mq_hw_ctx __rcu **queue_hw_ctx; unsigned int nr_hw_queues; struct backing_dev_info *backing_dev_info; -- 2.20.1