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Reinstate some of "swiotlb: rework "fix info leak with DMA_FROM_DEVICE""

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Halil Pasic points out [1] that the full revert of that commit (revert
in bddac7c1e0), and that a partial revert that only reverts the
problematic case, but still keeps some of the cleanups is probably
better.  

And that partial revert [2] had already been verified by Oleksandr
Natalenko to also fix the issue, I had just missed that in the long
discussion.

So let's reinstate the cleanups from commit aa6f8dcbab ("swiotlb:
rework "fix info leak with DMA_FROM_DEVICE""), and effectively only
revert the part that caused problems.

Link: https://lore.kernel.org/all/20220328013731.017ae3e3.pasic@linux.ibm.com/ [1]
Link: https://lore.kernel.org/all/20220324055732.GB12078@lst.de/ [2]
Link: https://lore.kernel.org/all/4386660.LvFx2qVVIh@natalenko.name/ [3]
Suggested-by: Halil Pasic <pasic@linux.ibm.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: Christoph Hellwig" <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds
2022-03-28 11:37:05 -07:00
parent ae085d7f93
commit 901c7280ca
3 changed files with 8 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/dma/swiotlb.c
+8 -4
View File
@@ -627,10 +627,14 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
for (i = 0; i < nr_slots(alloc_size + offset); i++)
mem->slots[index + i].orig_addr = slot_addr(orig_addr, i);
tlb_addr = slot_addr(mem->start, index) + offset;
if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
(!(attrs & DMA_ATTR_OVERWRITE) || dir == DMA_TO_DEVICE ||
dir == DMA_BIDIRECTIONAL))
swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE);
/*
* When dir == DMA_FROM_DEVICE we could omit the copy from the orig
* to the tlb buffer, if we knew for sure the device will
* overwirte the entire current content. But we don't. Thus
* unconditional bounce may prevent leaking swiotlb content (i.e.
* kernel memory) to user-space.
*/
swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE);
return tlb_addr;
}