[PATCH] swiotlb: manipulate orig_addr when tlb_addr has offset

[Linus Torvalds]

in case of driver wants to sync part of ranges with offset,
swiotlb_tbl_sync_single() copies from orig_addr base to tlb_addr with
offset and ends up with data mismatch.

It was removed from
"swiotlb: don't modify orig_addr in swiotlb_tbl_sync_single",
but said logic has to be added back in.

[From Linus's email:
That commit which the removed the offset calculation entirely, because the old

        (unsigned long)tlb_addr & (IO_TLB_SIZE - 1)

was wrong, but instead of removing it, I think it should have just
fixed it to be

        (tlb_addr - mem->start) & (IO_TLB_SIZE - 1);

instead. That way the slot offset always matches the slot index calculation.]

The use-case that drivers are hitting is as follow:

1. Get dma_addr_t from dma_map_single()

dma_addr_t tlb_addr = dma_map_single(dev, vaddr, vsize, DMA_TO_DEVICE);

    |<---------------vsize------------->|
    +-----------------------------------+
    |                                   | original buffer
    +-----------------------------------+
  vaddr

 swiotlb_align_offset
     |<----->|<---------------vsize------------->|
     +-------+-----------------------------------+
     |       |                                   | swiotlb buffer
     +-------+-----------------------------------+
          tlb_addr

2. Do something
3. Sync dma_addr_t through dma_sync_single_for_device(..)

dma_sync_single_for_device(dev, tlb_addr + offset, size, DMA_TO_DEVICE);

  Error case.
    Copy data to original buffer but it is from base addr (instead of
  base addr + offset) in original buffer:

 swiotlb_align_offset
     |<----->|<- offset ->|<- size ->|
     +-------+-----------------------------------+
     |       |            |##########|           | swiotlb buffer
     +-------+-----------------------------------+
          tlb_addr

    |<- size ->|
    +-----------------------------------+
    |##########|                        | original buffer
    +-----------------------------------+
  vaddr

The fix is to copy the data to the original buffer and take into
account the offset, like so:

 swiotlb_align_offset
     |<----->|<- offset ->|<- size ->|
     +-------+-----------------------------------+
     |       |            |##########|           | swiotlb buffer
     +-------+-----------------------------------+
          tlb_addr

    |<- offset ->|<- size ->|
    +-----------------------------------+
    |            |##########|           | original buffer
    +-----------------------------------+
  vaddr

[This patch text is from Bumyong's email; and his solution was very close
to Linus's, so incorporating his text]

Fixes: 16fc3cef33a0 ("swiotlb: don't modify orig_addr in swiotlb_tbl_sync_single")
Signed-off-by: Bumyong Lee <bumyong.lee@xxxxxxxxxxx>
Signed-off-by: Chanho Park <chanho61.park@xxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reported-by: Dominique MARTINET <dominique.martinet@xxxxxxxxxxxxxxxxx>
Reported-by: Horia Geantă <horia.geanta@xxxxxxx>
Tested-by: Horia Geantă <horia.geanta@xxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
CC: stable@xxxxxxxxxxxxxxx
Signed-off-by: Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>
---
 kernel/dma/swiotlb.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 8ca7d50..dc438b5 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -342,6 +342,7 @@ static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size
 {
 	struct io_tlb_mem *mem = io_tlb_default_mem;
 	int index = (tlb_addr - mem->start) >> IO_TLB_SHIFT;
+	unsigned int offset = (tlb_addr - mem->start) & (IO_TLB_SIZE - 1);
 	phys_addr_t orig_addr = mem->slots[index].orig_addr;
 	size_t alloc_size = mem->slots[index].alloc_size;
 	unsigned long pfn = PFN_DOWN(orig_addr);
@@ -350,6 +351,14 @@ static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size
 	if (orig_addr == INVALID_PHYS_ADDR)
 		return;
 
+	if (offset > alloc_size) {
+		dev_WARN_ONCE(dev, 1,
+			"Buffer overflow detected. Offset: %lu. Mapping size: %zu.\n",
+			offset, size);
+		return;
+	}
+	alloc_size -= offset;
+	orig_addr += offset;
 	if (size > alloc_size) {
 		dev_WARN_ONCE(dev, 1,
 			"Buffer overflow detected. Allocation size: %zu. Mapping size: %zu.\n",
-- 
1.8.3.1


--uNcz+wGozi5IAMFR
Content-Type: text/plain; charset=utf-8
Content-Disposition: attachment;
	filename="0001-swiotlb-manipulate-orig_addr-when-tlb_addr-has-offse.patch"
Content-Transfer-Encoding: 8bit