From 74c9c9134bf8d8a6d5c5683f60262eed3d6fb5ac Mon Sep 17 00:00:00 2001 From: Jeff Moyer Date: Wed, 29 Jul 2015 10:22:50 -0400 Subject: [PATCH] mtip32x: fix regression introduced by blk-mq per-hctx flush Hi, After commit f70ced091707 (blk-mq: support per-distpatch_queue flush machinery), the mtip32xx driver may oops upon module load due to walking off the end of an array in mtip_init_cmd. On initialization of the flush_rq, init_request is called with request_index >= the maximum queue depth the driver supports. For mtip32xx, this value is used to index into an array. What this means is that the driver will walk off the end of the array, and either oops or cause random memory corruption. The problem is easily reproduced by doing modprobe/rmmod of the mtip32xx driver in a loop. I can typically reproduce the problem in about 30 seconds. Now, in the case of mtip32xx, it actually doesn't support flush/fua, so I think we can simply return without doing anything. In addition, no other mq-enabled driver does anything with the request_index passed into init_request(), so no other driver is affected. However, I'm not really sure what is expected of drivers. Ming, what did you envision drivers would do when initializing the flush requests? Signed-off-by: Jeff Moyer Signed-off-by: Jens Axboe --- drivers/block/mtip32xx/mtip32xx.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c index 4a2ef09e6704..f504232c1ee7 100644 --- a/drivers/block/mtip32xx/mtip32xx.c +++ b/drivers/block/mtip32xx/mtip32xx.c @@ -3756,6 +3756,14 @@ static int mtip_init_cmd(void *data, struct request *rq, unsigned int hctx_idx, struct mtip_cmd *cmd = blk_mq_rq_to_pdu(rq); u32 host_cap_64 = readl(dd->mmio + HOST_CAP) & HOST_CAP_64; + /* + * For flush requests, request_idx starts at the end of the + * tag space. Since we don't support FLUSH/FUA, simply return + * 0 as there's nothing to be done. + */ + if (request_idx >= MTIP_MAX_COMMAND_SLOTS) + return 0; + cmd->command = dmam_alloc_coherent(&dd->pdev->dev, CMD_DMA_ALLOC_SZ, &cmd->command_dma, GFP_KERNEL); if (!cmd->command) -- 2.20.1