linux-kernel - [PATCH] nvmet: fix mar and mor off-by-one errors

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Message-Id: <20220905122116.2678206-1-Dennis.Maisenbacher@wdc.com>
Date:   Mon,  5 Sep 2022 14:21:16 +0200
From:   Dennis Maisenbacher <Dennis.Maisenbacher@....com>
To:     linux-nvme@...ts.infradead.org
Cc:     Dennis Maisenbacher <dennis.maisenbacher@....com>,
        Niklas Cassel <niklas.cassel@....com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Chaitanya Kulkarni <kch@...dia.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] nvmet: fix mar and mor off-by-one errors

From: Dennis Maisenbacher <dennis.maisenbacher@....com>

Maximum Active Resources (MAR) and Maximum Open Resources (MOR) are 0's
based vales where a value of 0xffffffff indicates that there is no limit.

Cast the unsigned int values that are returned by bdev_max_open_zones and
bdev_max_active_zones into u32 vales which need to be decremented as the
returned values of the block layer helpers are not 0's based.
The cast to u32 is necessary because the size of unsigned int is
architecture dependent and a 0 reported by the block layer helpers
indicates no limit, thus it needs to be converted to 0xffffffff which
happens by underflowing the u32.

Suggested-by: Niklas Cassel <niklas.cassel@....com>
Signed-off-by: Dennis Maisenbacher <dennis.maisenbacher@....com>
---
 drivers/nvme/target/zns.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/zns.c b/drivers/nvme/target/zns.c
index c7ef69f29fe4..606f21ee21bf 100644
--- a/drivers/nvme/target/zns.c
+++ b/drivers/nvme/target/zns.c
@@ -100,6 +100,7 @@ void nvmet_execute_identify_cns_cs_ns(struct nvmet_req *req)
 	struct nvme_id_ns_zns *id_zns;
 	u64 zsze;
 	u16 status;
+	u32 mar, mor;
 
 	if (le32_to_cpu(req->cmd->identify.nsid) == NVME_NSID_ALL) {
 		req->error_loc = offsetof(struct nvme_identify, nsid);
@@ -130,8 +131,10 @@ void nvmet_execute_identify_cns_cs_ns(struct nvmet_req *req)
 	zsze = (bdev_zone_sectors(req->ns->bdev) << 9) >>
 					req->ns->blksize_shift;
 	id_zns->lbafe[0].zsze = cpu_to_le64(zsze);
-	id_zns->mor = cpu_to_le32(bdev_max_open_zones(req->ns->bdev));
-	id_zns->mar = cpu_to_le32(bdev_max_active_zones(req->ns->bdev));
+	mor = bdev_max_open_zones(req->ns->bdev);
+	id_zns->mor = cpu_to_le32(--mor);
+	mar = bdev_max_active_zones(req->ns->bdev);
+	id_zns->mar = cpu_to_le32(--mar);
 
 done:
 	status = nvmet_copy_to_sgl(req, 0, id_zns, sizeof(*id_zns));
-- 
2.25.1