From: Vlastimil Babka <[email protected]> commit 49f2d2419d60a103752e5fbaf158cf8d07c0d884 upstream.
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_+6e...@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]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- mm/slab_common.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1303,7 +1303,8 @@ void __init create_kmalloc_caches(slab_f 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
