The patch titled
Subject: usercopy: mark dma-kmalloc caches as usercopy caches
has been added to the -mm tree. Its filename is
usercopy-mark-dma-kmalloc-caches-as-usercopy-caches.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/usercopy-mark-dma-kmalloc-caches-as-usercopy-caches.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/usercopy-mark-dma-kmalloc-caches-as-usercopy-caches.patch
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------------------------------------------------------
From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: 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/bfca96db-bbd0-d958-7732-76e36c667c68@xxxxxxx/
[3] https://lore.kernel.org/kernel-hardening/CAG48ez1a4waGk9kB0WLaSbs4muSoK0AYAVk8=XYaKj4_+6e6Hg@xxxxxxxxxxxxxx/
Link: http://lkml.kernel.org/r/7d810f6d-8085-ea2f-7805-47ba3842dc50@xxxxxxx
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Acked-by: Jiri Slaby <jslaby@xxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Christopher Lameter <cl@xxxxxxxxx>
Cc: Julian Wiedmann <jwi@xxxxxxxxxxxxx>
Cc: Ursula Braun <ubraun@xxxxxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: David Windsor <dave@xxxxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Laura Abbott <labbott@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Cc: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Luis de Bethencourt <luisbg@xxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Matthew Garrett <mjg59@xxxxxxxxxx>
Cc: Michal Kubecek <mkubecek@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slab_common.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/mm/slab_common.c~usercopy-mark-dma-kmalloc-caches-as-usercopy-caches
+++ a/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
_
Patches currently in -mm which might be from vbabka@xxxxxxx are
usercopy-mark-dma-kmalloc-caches-as-usercopy-caches.patch
mm-dump_page-do-not-crash-with-invalid-mapping-pointer.patch
