linux-kernel - [PATCH 5.9 633/757] nvmet: limit passthru MTDS by BIO_MAX

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Date:   Tue, 27 Oct 2020 14:54:43 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Christoph Hellwig <hch@....de>,
        Logan Gunthorpe <logang@...tatee.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Chaitanya Kulkarni <chaitanya.kulkarni@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.9 633/757] nvmet: limit passthru MTDS by BIO_MAX_PAGES

From: Logan Gunthorpe <logang@...tatee.com>

[ Upstream commit df06047d54276f73782c9d97882b305fca745d3f ]

nvmet_passthru_map_sg() only supports mapping a single BIO, not a chain
so the effective maximum transfer should also be limitted by
BIO_MAX_PAGES (presently this works out to 1MB).

For PCI passthru devices the max_sectors would typically be more
limitting than BIO_MAX_PAGES, but this may not be true for all passthru
devices.

Fixes: c1fef73f793b ("nvmet: add passthru code to process commands")
Suggested-by: Christoph Hellwig <hch@....de>
Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
Cc: Christoph Hellwig <hch@....de>
Cc: Sagi Grimberg <sagi@...mberg.me>
Cc: Chaitanya Kulkarni <chaitanya.kulkarni@....com>
Signed-off-by: Christoph Hellwig <hch@....de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/nvme/target/passthru.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/passthru.c b/drivers/nvme/target/passthru.c
index dacfa7435d0b2..1ab88df3310f6 100644
--- a/drivers/nvme/target/passthru.c
+++ b/drivers/nvme/target/passthru.c
@@ -26,7 +26,7 @@ static u16 nvmet_passthru_override_id_ctrl(struct nvmet_req *req)
 	struct nvme_ctrl *pctrl = ctrl->subsys->passthru_ctrl;
 	u16 status = NVME_SC_SUCCESS;
 	struct nvme_id_ctrl *id;
-	u32 max_hw_sectors;
+	int max_hw_sectors;
 	int page_shift;
 
 	id = kzalloc(sizeof(*id), GFP_KERNEL);
@@ -48,6 +48,13 @@ static u16 nvmet_passthru_override_id_ctrl(struct nvmet_req *req)
 	max_hw_sectors = min_not_zero(pctrl->max_segments << (PAGE_SHIFT - 9),
 				      pctrl->max_hw_sectors);
 
+	/*
+	 * nvmet_passthru_map_sg is limitted to using a single bio so limit
+	 * the mdts based on BIO_MAX_PAGES as well
+	 */
+	max_hw_sectors = min_not_zero(BIO_MAX_PAGES << (PAGE_SHIFT - 9),
+				      max_hw_sectors);
+
 	page_shift = NVME_CAP_MPSMIN(ctrl->cap) + 12;
 
 	id->mdts = ilog2(max_hw_sectors) + 9 - page_shift;
-- 
2.25.1