The condition in xen_swiotlb_free_coherent() for deciding whether to call xen_destroy_contiguous_region() is wrong: in case the region to be freed is not contiguous calling xen_destroy_contiguous_region() is the wrong thing to do: it would result in inconsistent mappings of multiple PFNs to the same MFN. This will lead to various strange crashes or data corruption.
Instead of calling xen_destroy_contiguous_region() in that case a warning should be issued as that situation should never occur.
Cc: stable@vger.kernel.org Signed-off-by: Juergen Gross jgross@suse.com --- drivers/xen/swiotlb-xen.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c index 877baf2a94f4..42a3924e6d91 100644 --- a/drivers/xen/swiotlb-xen.c +++ b/drivers/xen/swiotlb-xen.c @@ -360,8 +360,8 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr, /* Convert the size to actually allocated. */ size = 1UL << (order + XEN_PAGE_SHIFT);
- if (((dev_addr + size - 1 <= dma_mask)) || - range_straddles_page_boundary(phys, size)) + if ((dev_addr + size - 1 <= dma_mask) && + !WARN_ON(range_straddles_page_boundary(phys, size))) xen_destroy_contiguous_region(phys, order);
xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs);
On 4/23/19 6:54 AM, Juergen Gross wrote:
The condition in xen_swiotlb_free_coherent() for deciding whether to call xen_destroy_contiguous_region() is wrong: in case the region to be freed is not contiguous calling xen_destroy_contiguous_region() is the wrong thing to do: it would result in inconsistent mappings of multiple PFNs to the same MFN. This will lead to various strange crashes or data corruption.
Instead of calling xen_destroy_contiguous_region() in that case a warning should be issued as that situation should never occur.
Cc: stable@vger.kernel.org Signed-off-by: Juergen Gross jgross@suse.com
Reviewed-by: Boris Ostrovsky boris.ostrovsky@oracle.com
On 23.04.19 at 12:54, jgross@suse.com wrote:
--- a/drivers/xen/swiotlb-xen.c +++ b/drivers/xen/swiotlb-xen.c @@ -360,8 +360,8 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr, /* Convert the size to actually allocated. */ size = 1UL << (order + XEN_PAGE_SHIFT);
- if (((dev_addr + size - 1 <= dma_mask)) ||
range_straddles_page_boundary(phys, size))
- if ((dev_addr + size - 1 <= dma_mask) &&
!WARN_ON(range_straddles_page_boundary(phys, size)))
On the allocation side we have
if (((dev_addr + size - 1 <= dma_mask)) && !range_straddles_page_boundary(phys, size)) *dma_handle = dev_addr; else { if (xen_create_contiguous_region(phys, order, fls64(dma_mask), dma_handle) != 0) { xen_free_coherent_pages(hwdev, size, ret, (dma_addr_t)phys, attrs); return NULL; } }
which is (as far as the function call is concerned)
if ((dev_addr + size - 1 > dma_mask) || range_straddles_page_boundary(phys, size)) xen_create_contiguous_region(...);
So I don't think your transformation is correct. Even worse, both parts of the condition in xen_swiotlb_free_coherent() act on an address that is the _result_ of the prior xen_create_contiguous_region(), i.e. the address should always match _both_ criteria anyway. Whereas what you really want is undo the xen_create_contiguous_region() only when it actually was called. Otherwise you also shatter contiguous allocations that were contiguous already for other reasons (perhaps just luck).
Jan
linux-stable-mirror@lists.linaro.org
-
Boris Ostrovsky -
Jan Beulich -
Juergen Gross