From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH v11 08/14] net, arm64: untag user pointers in
 tcp_zerocopy_receive
Date: Fri, 15 Mar 2019 13:03:30 -0700
Message-ID: <04c5b2de-7fde-7625-9d42-228160879ea0__21969.2621076078$1552680226$gmane$org@gmail.com>
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To: Andrey Konovalov <andreyknvl@google.com>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, Mark Rutland <mark.rutland@arm.com>, Robin Murphy <robin.murphy@arm.com>, Kees Cook <keescook@chromium.org>, Kate Stewart <kstewart@linuxfoundation.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@kernel.org>, "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>, Shuah Khan <shuah@kernel.org>, Vincenzo Frascino <vincenzo.frascino@arm.com>, Eric Dumazet <edumazet@google.com>, "David S. Miller" <davem@davemloft.net>, Alexei Starovoitov <ast@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>, Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Arnaldo Carvalho de Melo <acme@kernel.org>, linux-arm-kernel@lists.infradead.orglin
Cc: Kevin Brodsky <kevin.brodsky@arm.com>, Chintan Pandya <cpandya@codeaurora.org>, Jacob Bramley <Jacob.Bramley@arm.com>, Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>, Szabolcs Nagy <Szabolcs.Nagy@arm.com>, Lee Smith <Lee.Smith@arm.com>, Kostya Serebryany <kcc@google.com>, Dmitry Vyukov <dvyukov@google.com>, Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>, Luc Van Oostenryck <luc.vanoostenryck@gmail.com>, Dave Martin <Dave.Martin@arm.com>, Evgeniy Stepanov <eugenis@google.com>
List-Id: linux-arch.vger.kernel.org



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;
>  
>