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swiotlb: skip swiotlb_bounce when orig_addr is zero

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After patch ddbd89deb7d3 ("swiotlb: fix info leak with DMA_FROM_DEVICE"),
swiotlb_bounce will be called in swiotlb_tbl_map_single unconditionally.
This requires that the physical address must be valid, which is not always
true on stable-4.19 or earlier version.
On stable-4.19, swiotlb_alloc_buffer will call swiotlb_tbl_map_single with
orig_addr equal to zero, which cause such a panic:

Unable to handle kernel paging request at virtual address ffffb77a40000000
...
pc : __memcpy+0x100/0x180
lr : swiotlb_bounce+0x74/0x88
...
Call trace:
 __memcpy+0x100/0x180
 swiotlb_tbl_map_single+0x2c8/0x338
 swiotlb_alloc+0xb4/0x198
 __dma_alloc+0x84/0x1d8
 ...

On stable-4.9 and stable-4.14, swiotlb_alloc_coherent wille call map_single
with orig_addr equal to zero, which can cause same panic.

Fix this by skipping swiotlb_bounce when orig_addr is zero.

Fixes: ddbd89deb7d3 ("swiotlb: fix info leak with DMA_FROM_DEVICE")
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Liu Shixin 2022-06-30 19:32:25 +08:00 committed by Greg Kroah-Hartman
parent 6af88cc6e4
commit 87fe5447ea
1 changed files with 2 additions and 1 deletions
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3
lib/swiotlb.c
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@ -607,7 +607,8 @@ found:
* unconditional bounce may prevent leaking swiotlb content (i.e.
* kernel memory) to user-space.
*/
swiotlb_bounce(orig_addr, tlb_addr, size, DMA_TO_DEVICE);
if (orig_addr)
swiotlb_bounce(orig_addr, tlb_addr, size, DMA_TO_DEVICE);
return tlb_addr;
}
EXPORT_SYMBOL_GPL(swiotlb_tbl_map_single);