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SubjectRe: [PATCH] drivers/misc/vmw_vmci: restrict too big queue size in qp_host_alloc_queue
On Sat, Feb 06, 2021 at 11:34:09AM +0600, Sabyrzhan Tasbolatov wrote:
> syzbot found WARNING in qp_broker_alloc[1] in qp_host_alloc_queue()
> when num_pages is 0x100001, giving queue_size + queue_page_size
> bigger than KMALLOC_MAX_SIZE for kzalloc(), resulting order >= MAX_ORDER
> condition.
>
> queue_size + queue_page_size=0x8000d8, where KMALLOC_MAX_SIZE=0x400000.
>
>
> FYI, I've also noticed in vmci_queue_pair.c other SLAB allocations with no
> length check that might exceed KMALLOC_MAX_SIZE as well,
> but syzbot doesn't have reproduces for them.
>
> in qp_alloc_ppn_set():
> produce_ppns =
> kmalloc_array(num_produce_pages, sizeof(*produce_ppns),
> GFP_KERNEL);
> [..]
> consume_ppns =
> kmalloc_array(num_consume_pages, sizeof(*consume_ppns),
> GFP_KERNEL);
> [..]
> in qp_alloc_hypercall():
> msg_size = sizeof(*alloc_msg) +
> (size_t) entry->num_ppns * ppn_size;
> alloc_msg = kmalloc(msg_size, GFP_KERNEL);
> [..]
> in qp_broker_create():
> entry->local_mem = kcalloc(QPE_NUM_PAGES(entry->qp),
> PAGE_SIZE, GFP_KERNEL);
>
> [1]
> Call Trace:
> alloc_pages include/linux/gfp.h:547 [inline]
> kmalloc_order+0x40/0x130 mm/slab_common.c:837
> kmalloc_order_trace+0x15/0x70 mm/slab_common.c:853
> kmalloc_large include/linux/slab.h:481 [inline]
> __kmalloc+0x257/0x330 mm/slub.c:3959
> kmalloc include/linux/slab.h:557 [inline]
> kzalloc include/linux/slab.h:682 [inline]
> qp_host_alloc_queue drivers/misc/vmw_vmci/vmci_queue_pair.c:540 [inline]
> qp_broker_create drivers/misc/vmw_vmci/vmci_queue_pair.c:1351 [inline]
> qp_broker_alloc+0x936/0x2740 drivers/misc/vmw_vmci/vmci_queue_pair.c:1739
>
> Reported-by: syzbot+15ec7391f3d6a1a7cc7d@syzkaller.appspotmail.com
> Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
> ---
> drivers/misc/vmw_vmci/vmci_queue_pair.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/misc/vmw_vmci/vmci_queue_pair.c b/drivers/misc/vmw_vmci/vmci_queue_pair.c
> index c49065887e8f..f6af406fda80 100644
> --- a/drivers/misc/vmw_vmci/vmci_queue_pair.c
> +++ b/drivers/misc/vmw_vmci/vmci_queue_pair.c
> @@ -537,6 +537,11 @@ static struct vmci_queue *qp_host_alloc_queue(u64 size)
>
> queue_page_size = num_pages * sizeof(*queue->kernel_if->u.h.page);
>
> + if (queue_size + queue_page_size > KMALLOC_MAX_SIZE) {
> + pr_warn("too big queue to allocate\n");

As this is controllable by userspace, you just provided a way to flood
the kernel logs.

Please make this a dev_dbg() call instead, if you really want to see it.
Otherwise just return NULL, no need to report anything, right?

thanks,

greg k-h

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