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Subject[PATCH 4.19 155/219] nvme: Discard workaround for non-conformant devices
Date
From: Eduard Hasenleithner <eduard@hasenleithner.at>

[ Upstream commit 530436c45ef2e446c12538a400e465929a0b3ade ]

Users observe IOMMU related errors when performing discard on nvme from
non-compliant nvme devices reading beyond the end of the DMA mapped
ranges to discard.

Two different variants of this behavior have been observed: SM22XX
controllers round up the read size to a multiple of 512 bytes, and Phison
E12 unconditionally reads the maximum discard size allowed by the spec
(256 segments or 4kB).

Make nvme_setup_discard unconditionally allocate the maximum DSM buffer
so the driver DMA maps a memory range that will always succeed.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=202665 many
Signed-off-by: Eduard Hasenleithner <eduard@hasenleithner.at>
[changelog, use existing define, kernel coding style]
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/nvme/host/core.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index b2d9bd564960..b7bd89b3b2f9 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -551,8 +551,14 @@ static blk_status_t nvme_setup_discard(struct nvme_ns *ns, struct request *req,
struct nvme_dsm_range *range;
struct bio *bio;

- range = kmalloc_array(segments, sizeof(*range),
- GFP_ATOMIC | __GFP_NOWARN);
+ /*
+ * Some devices do not consider the DSM 'Number of Ranges' field when
+ * determining how much data to DMA. Always allocate memory for maximum
+ * number of segments to prevent device reading beyond end of buffer.
+ */
+ static const size_t alloc_size = sizeof(*range) * NVME_DSM_MAX_RANGES;
+
+ range = kzalloc(alloc_size, GFP_ATOMIC | __GFP_NOWARN);
if (!range) {
/*
* If we fail allocation our range, fallback to the controller
@@ -593,7 +599,7 @@ static blk_status_t nvme_setup_discard(struct nvme_ns *ns, struct request *req,

req->special_vec.bv_page = virt_to_page(range);
req->special_vec.bv_offset = offset_in_page(range);
- req->special_vec.bv_len = sizeof(*range) * segments;
+ req->special_vec.bv_len = alloc_size;
req->rq_flags |= RQF_SPECIAL_PAYLOAD;

return BLK_STS_OK;
--
2.20.1


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