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SubjectRe: [PATCH] net/qrtr: restrict length in qrtr_tun_write_iter()
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On 2/21/21 1:39 PM, Sabyrzhan Tasbolatov wrote:
>> Do we really expect to accept huge lengths here ?
>
> Sorry for late response but I couldnt find any reference to the max
> length of incoming data for qrtr TUN interface.
>
>> qrtr_endpoint_post() will later attempt a netdev_alloc_skb() which will need
>> some extra space (for struct skb_shared_info)
>
> Thanks, you're right, qrtr_endpoint_post() will alloc another slab buffer.
> We can check the length of skb allocation but we need to do following:
>
> int qrtr_endpoint_post(.., const void *data, size_t len)
> {
> ..
> when QRTR_PROTO_VER_1:
> hdrlen = sizeof(*data);
> when QRTR_PROTO_VER_2:
> hdrlen = sizeof(*data) + data->optlen;
>
> len = (KMALLOC_MAX_SIZE - hdrlen) % data->size;
> skb = netdev_alloc_skb(NULL, len);
> ..
> skb_put_data(skb, data + hdrlen, size);
>
>
> So it requires refactoring as in qrtr_tun_write_iter() we just allocate and
> pass it to qrtr_endpoint_post() and there
> we need to do len calculation as above *before* netdev_alloc_skb(NULL, len).
>
> Perhaps there is a nicer solution though.
>

A protocol requiring contiguous physical memory allocations of up to KMALLOC_MAX_SIZE
bytes would be really unreliable.

I suggest we simply limit the allocations to 64KB, unless qrtr maintainers shout,
or start implementing scatter gather.





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