blk-mq: Avoid race condition with uninitialized requests
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@vger.kernel.org Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com> Reported-by: Paulo De Rezende Pinatti <ppinatti@linux.vnet.ibm.com> Tested-by: Paulo De Rezende Pinatti <ppinatti@linux.vnet.ibm.com> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Jens Axboe <axboe@fb.com>
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@ -203,7 +203,6 @@ __blk_mq_alloc_request(struct blk_mq_alloc_data *data, int rw)
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if (tag != BLK_MQ_TAG_FAIL) {
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rq = data->hctx->tags->rqs[tag];
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rq->cmd_flags = 0;
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if (blk_mq_tag_busy(data->hctx)) {
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rq->cmd_flags = REQ_MQ_INFLIGHT;
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atomic_inc(&data->hctx->nr_active);
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@ -258,6 +257,7 @@ static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx,
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if (rq->cmd_flags & REQ_MQ_INFLIGHT)
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atomic_dec(&hctx->nr_active);
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rq->cmd_flags = 0;
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clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
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blk_mq_put_tag(hctx, tag, &ctx->last_tag);
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@ -1410,6 +1410,8 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set,
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left -= to_do * rq_size;
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for (j = 0; j < to_do; j++) {
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tags->rqs[i] = p;
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tags->rqs[i]->atomic_flags = 0;
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tags->rqs[i]->cmd_flags = 0;
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if (set->ops->init_request) {
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if (set->ops->init_request(set->driver_data,
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tags->rqs[i], hctx_idx, i,
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