usercopy: mark dma-kmalloc caches as usercopy caches

We have seen a "usercopy: Kernel memory overwrite attempt detected to
SLUB object 'dma-kmalloc-1 k' (offset 0, size 11)!" error on s390x, as
IUCV uses kmalloc() with __GFP_DMA because of memory address
restrictions.  The issue has been discussed [2] and it has been noted
that if all the kmalloc caches are marked as usercopy, there's little
reason not to mark dma-kmalloc caches too.  The 'dma' part merely means
that __GFP_DMA is used to restrict memory address range.

As Jann Horn put it [3]:
 "I think dma-kmalloc slabs should be handled the same way as normal
  kmalloc slabs. When a dma-kmalloc allocation is freshly created, it is
  just normal kernel memory - even if it might later be used for DMA -,
  and it should be perfectly fine to copy_from_user() into such
  allocations at that point, and to copy_to_user() out of them at the
  end. If you look at the places where such allocations are created, you
  can see things like kmemdup(), memcpy() and so on - all normal
  operations that shouldn't conceptually be different from usercopy in
  any relevant way."

Thus this patch marks the dma-kmalloc-* caches as usercopy.

[1] https://bugzilla.suse.com/show_bug.cgi?id=1156053
[2] https://lore.kernel.org/kernel-hardening/[email protected]/
[3] https://lore.kernel.org/kernel-hardening/CAG48ez1a4waGk9kB0WLaSbs4muSoK0AYAVk8=XYaKj4_+6e6Hg@mail.gmail.com/

Signed-off-by: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Christian Borntraeger <[email protected]>
Acked-by: Jiri Slaby <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Christopher Lameter <[email protected]>
Cc: Julian Wiedmann <[email protected]>
Cc: Ursula Braun <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: David Windsor <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Laura Abbott <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: "Martin K. Petersen" <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Christoffer Dall <[email protected]>
Cc: Dave Kleikamp <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Luis de Bethencourt <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Matthew Garrett <[email protected]>
Cc: Michal Kubecek <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 2 insertions, 1 deletions

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 23c7500eea7d..9e72ba224175 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1303,7 +1303,8 @@ void __init create_kmalloc_caches(slab_flags_t flags)
 			kmalloc_caches[KMALLOC_DMA][i] = create_kmalloc_cache(
 				kmalloc_info[i].name[KMALLOC_DMA],
 				kmalloc_info[i].size,
-				SLAB_CACHE_DMA | flags, 0, 0);
+				SLAB_CACHE_DMA | flags, 0,
+				kmalloc_info[i].size);
 		}
 	}
 #endif