This patch should fix the bug reported in https://lkml.org/lkml/2014/9/11/249. We have to initialize at least the atomic_flags and the cmd_flags when allocating storage for the requests. Otherwise blk_mq_timeout_check() might dereference uninitialized pointers when racing with the creation of a request. Also move the reset of cmd_flags for the initializing code to the point where a request is freed. So we will never end up with pending flush request indicators that might trigger dereferences of invalid pointers in blk_mq_timeout_check(). Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: David Hildenbrand <dahi@xxxxxxxxxxxxxxxxxx> --- block/blk-mq.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 383ea0c..eed6340 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -203,7 +203,6 @@ __blk_mq_alloc_request(struct blk_mq_alloc_data *data, int rw) if (tag != BLK_MQ_TAG_FAIL) { rq = data->hctx->tags->rqs[tag]; - rq->cmd_flags = 0; if (blk_mq_tag_busy(data->hctx)) { rq->cmd_flags = REQ_MQ_INFLIGHT; atomic_inc(&data->hctx->nr_active); @@ -258,6 +257,7 @@ static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx, if (rq->cmd_flags & REQ_MQ_INFLIGHT) atomic_dec(&hctx->nr_active); + rq->cmd_flags = 0; clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags); blk_mq_put_tag(hctx, tag, &ctx->last_tag); @@ -1404,6 +1404,8 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set, left -= to_do * rq_size; for (j = 0; j < to_do; j++) { tags->rqs[i] = p; + tags->rqs[i]->atomic_flags = 0; + tags->rqs[i]->cmd_flags = 0; if (set->ops->init_request) { if (set->ops->init_request(set->driver_data, tags->rqs[i], hctx_idx, i, -- 1.8.5.5 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
