Messages in this thread Patch in this message | | | Date | Wed, 18 Mar 2015 13:36:32 -0700 | From | Sam Bradshaw <> | Subject | [PATCH] blkmq: Fix NULL pointer deref when all reserved tags in use |
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When allocating from the reserved tags pool, bt_get() is called with a NULL hctx. If all tags are in use, the hw queue is kicked to push out any pending IO, potentially freeing tags, and tag allocation is retried. The problem is that blk_mq_run_hw_queue() doesn't check for a NULL hctx. This patch fixes that bug.
An alternative implementation might skip kicking the queue for reserved tags and go right to io_schedule() but we chose to keep it simple.
Tested by hammering mtip32xx with concurrent smartctl/hdparm.
Signed-off-by: Sam Bradshaw <sbradshaw@micron.com> Signed-off-by: Selvan Mani <smani@micron.com> --- block/blk-mq.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c index 59fa239..0471af6 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -887,7 +887,7 @@ static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx) void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async) { - if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state) || + if (unlikely(!hctx || test_bit(BLK_MQ_S_STOPPED, &hctx->state) || !blk_mq_hw_queue_mapped(hctx))) return; -- 1.7.1
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