On 02.06.20 22:10, Andrew Morton wrote: > 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> We have also seen this with other drivers (vmur). Shouldnt this also go via stable? > 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@xxxxxxxxxxx> > 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 > _ >
