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Subject[PATCH] null_blk: mem garbage on NUMA systems during init
Date
For NUMA systems, initializing the blk-mq layer and using per node hctx. We
initialize submit queues to 1, while blk-mq nr_hw_queues is initialized to the
number of NUMA nodes.

This makes the null_init_hctx function overwrite memory outside of what it
allocated. In my case it lead to writing garbage into struct request_queue's
mq_map.

Signed-off-by: Matias Bjorling <m@bjorling.me>
---
drivers/block/null_blk.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index ea192ec..f370fc1 100644
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -495,23 +495,23 @@ static int null_add_dev(void)

spin_lock_init(&nullb->lock);

+ if (queue_mode == NULL_Q_MQ && use_per_node_hctx)
+ submit_queues = nr_online_nodes;
+
if (setup_queues(nullb))
goto err;

if (queue_mode == NULL_Q_MQ) {
null_mq_reg.numa_node = home_node;
null_mq_reg.queue_depth = hw_queue_depth;
+ null_mq_reg.nr_hw_queues = submit_queues;

if (use_per_node_hctx) {
null_mq_reg.ops->alloc_hctx = null_alloc_hctx;
null_mq_reg.ops->free_hctx = null_free_hctx;
-
- null_mq_reg.nr_hw_queues = nr_online_nodes;
} else {
null_mq_reg.ops->alloc_hctx = blk_mq_alloc_single_hw_queue;
null_mq_reg.ops->free_hctx = blk_mq_free_single_hw_queue;
-
- null_mq_reg.nr_hw_queues = submit_queues;
}

nullb->q = blk_mq_init_queue(&null_mq_reg, nullb);
--
1.8.3.2


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