Re: [PATCH net v4 2/3] net: prevent rewrite of msg_name in sock_sendmsg()

[Pavel Begunkov <asml.silence@gmail.com>]

On 9/21/23 09:32, Paolo Abeni wrote:
> On Wed, 2023-09-20 at 09:28 -0400, Willem de Bruijn wrote:
>> Jordan Rife wrote:
>>> Callers of sock_sendmsg(), and similarly kernel_sendmsg(), in kernel
>>> space may observe their value of msg_name change in cases where BPF
>>> sendmsg hooks rewrite the send address. This has been confirmed to break
>>> NFS mounts running in UDP mode and has the potential to break other
>>> systems.
>>>
>>> This patch:
>>>
>>> 1) Creates a new function called __sock_sendmsg() with same logic as the
>>>     old sock_sendmsg() function.
>>> 2) Replaces calls to sock_sendmsg() made by __sys_sendto() and
>>>     __sys_sendmsg() with __sock_sendmsg() to avoid an unnecessary copy,
>>>     as these system calls are already protected.
>>> 3) Modifies sock_sendmsg() so that it makes a copy of msg_name if
>>>     present before passing it down the stack to insulate callers from
>>>     changes to the send address.
>>>
>>> Link: https://lore.kernel.org/netdev/20230912013332.2048422-1-jrife@google.com/
>>> Fixes: 1cedee13d25a ("bpf: Hooks for sys_sendmsg")
>>> Cc: stable@vger.kernel.org
>>> Signed-off-by: Jordan Rife <jrife@google.com>
>>
>> Reviewed-by: Willem de Bruijn <willemb@google.com>
> 
> CC Jens and Pavel, as I guess io_uring likely want to use
> __sock_sendmsg(), in a follow-up patch.

Yeah, likely so. Thanks Paolo, we'll take a look

-- 
Pavel Begunkov