From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
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/20220328013731.017ae3e3.pasic@xxxxxxxxxxxxx/ [1]
Link: https://lore.kernel.org/all/20220324055732.GB12078@xxxxxx/ [2]
Link: https://lore.kernel.org/all/4386660.LvFx2qVVIh@xxxxxxxxxxxxxx/ [3]
Suggested-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
Tested-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx>
Cc: Christoph Hellwig" <hch@xxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
Documentation/core-api/dma-attributes.rst | 8 --------
include/linux/dma-mapping.h | 8 --------
kernel/dma/swiotlb.c | 12 ++++++++----
3 files changed, 8 insertions(+), 20 deletions(-)
--- a/Documentation/core-api/dma-attributes.rst
+++ b/Documentation/core-api/dma-attributes.rst
@@ -130,11 +130,3 @@ accesses to DMA buffers in both privileg
subsystem that the buffer is fully accessible at the elevated privilege
level (and ideally inaccessible or at least read-only at the
lesser-privileged levels).
-
-DMA_ATTR_OVERWRITE
-------------------
-
-This is a hint to the DMA-mapping subsystem that the device is expected to
-overwrite the entire mapped size, thus the caller does not require any of the
-previous buffer contents to be preserved. This allows bounce-buffering
-implementations to optimise DMA_FROM_DEVICE transfers.
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -62,14 +62,6 @@
#define DMA_ATTR_PRIVILEGED (1UL << 9)
/*
- * This is a hint to the DMA-mapping subsystem that the device is expected
- * to overwrite the entire mapped size, thus the caller does not require any
- * of the previous buffer contents to be preserved. This allows
- * bounce-buffering implementations to optimise DMA_FROM_DEVICE transfers.
- */
-#define DMA_ATTR_OVERWRITE (1UL << 10)
-
-/*
* A dma_addr_t can hold any valid DMA or bus address for the platform. It can
* be given to a device to use as a DMA source or target. It is specific to a
* given device and there may be a translation between the CPU physical address
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -578,10 +578,14 @@ phys_addr_t swiotlb_tbl_map_single(struc
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;
}
Patches currently in stable-queue which might be from torvalds@xxxxxxxxxxxxxxxxxxxx are
queue-5.15/spi-fix-erroneous-sgs-value-with-min_t.patch
queue-5.15/ocfs2-fix-crash-when-mount-with-quota-enabled.patch
queue-5.15/revert-mm-madvise-skip-unmapped-vma-holes-passed-to-process_madvise.patch
queue-5.15/lib-uninline-simple_strntoull-as-well.patch
queue-5.15/mm-pages_alloc.c-don-t-create-zone_movable-beyond-the-end-of-a-node.patch
queue-5.15/kernel-resource-fix-kfree-of-bootmem-memory-again.patch
queue-5.15/selftests-vm-fix-clang-build-error-multiple-output-f.patch
queue-5.15/mm-invalidate-hwpoison-page-cache-page-in-fault-path.patch
queue-5.15/selftests-x86-fix-how-check_cc.sh-is-being-invoked.patch
queue-5.15/mempolicy-mbind_range-set_policy-after-vma_merge.patch
queue-5.15/fs-fd-tables-have-to-be-multiples-of-bits_per_long.patch
queue-5.15/mm-hwpoison-unmap-poisoned-page-before-invalidation.patch
queue-5.15/revert-swiotlb-rework-fix-info-leak-with-dma_from_device.patch
queue-5.15/mm-kfence-fix-missing-objcg-housekeeping-for-slab.patch
queue-5.15/kunit-make-kunit_test_timeout-compatible-with-commen.patch
queue-5.15/mm-kmemleak-reset-tag-when-compare-object-pointer.patch
queue-5.15/drivers-base-memory-add-memory-block-to-memory-group.patch
queue-5.15/revert-gpio-revert-regression-in-sysfs-gpio-gpiolib..patch
queue-5.15/reinstate-some-of-swiotlb-rework-fix-info-leak-with-dma_from_device.patch
queue-5.15/fs-fix-fd-table-size-alignment-properly.patch
queue-5.15/mm-fs-fix-lru_cache_disabled-race-in-bh_lru.patch
queue-5.15/ntfs-add-sanity-check-on-allocation-size.patch
queue-5.15/watch_queue-free-the-page-array-when-watch_queue-is-dismantled.patch
queue-5.15/mm-madvise-skip-unmapped-vma-holes-passed-to-process_madvise.patch
queue-5.15/mm-madvise-return-correct-bytes-advised-with-process_madvise.patch
