null_blk: mem garbage on NUMA systems during init

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>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index ea192ec029c4..f370fc13aea5 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);