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

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commit 901c7280ca0d5e2b4a8929fbe0bfb007ac2a6544 upstream.

Halil Pasic points out [1] that the full revert of that commit (revert
in bddac7c1e02b), 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 aa6f8dcbab47 ("swiotlb:
rework "fix info leak with DMA_FROM_DEVICE""), and effectively only
revert the part that caused problems.

Link: https://lore.kernel.org/all/[email protected]/ [1]
Link: https://lore.kernel.org/all/[email protected]/ [2]
Link: https://lore.kernel.org/all/[email protected]/ [3]
Suggested-by: Halil Pasic <[email protected]>
Tested-by: Oleksandr Natalenko <[email protected]>
Cc: Christoph Hellwig" <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
[OP: backport to 5.4: adjusted context]
Signed-off-by: Ovidiu Panait <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Linus Torvalds 2022-03-28 11:37:05 -07:00 • committed by Greg Kroah-Hartman
commit b2f140a9f9
3 changed files with 8 additions and 23 deletions
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13
kernel/dma/swiotlb.c
View file

@ -571,11 +571,14 @@ found:
*/
for (i = 0; i < nslots; i++)
io_tlb_orig_addr[index+i] = orig_addr + (i << IO_TLB_SHIFT);
if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
(!(attrs & DMA_ATTR_OVERWRITE) || dir == DMA_TO_DEVICE ||
dir == DMA_BIDIRECTIONAL))
swiotlb_bounce(orig_addr, 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(orig_addr, tlb_addr, mapping_size, DMA_TO_DEVICE);
return tlb_addr;
}