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 --- lib/swiotlb.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/swiotlb.c b/lib/swiotlb.c index bdc2b89870e3..e162cb464ee4 100644 --- a/lib/swiotlb.c +++ b/lib/swiotlb.c @@ -607,7 +607,8 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev, * 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);