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SubjectRe: [PATCH v11 08/14] net, arm64: untag user pointers in tcp_zerocopy_receive
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On 03/15/2019 12:51 PM, Andrey Konovalov wrote:
> This patch is a part of a series that extends arm64 kernel ABI to allow to
> pass tagged user pointers (with the top byte set to something else other
> than 0x00) as syscall arguments.
>
> tcp_zerocopy_receive() uses provided user pointers for vma lookups, which
> can only by done with untagged pointers.
>
> Untag user pointers in this function.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> ---
> net/ipv4/tcp.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 6baa6dc1b13b..89db3b4fc753 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -1758,6 +1758,8 @@ static int tcp_zerocopy_receive(struct sock *sk,
> int inq;
> int ret;
>
> + address = untagged_addr(address);
> +
> if (address & (PAGE_SIZE - 1) || address != zc->address)

The second test will fail, if the top bits are changed in address but not in zc->address

> return -EINVAL;
>
>

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