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Subject: Re: [PATCH] add param that allows bootline control of hardened
 usercopy
From:   Paolo Abeni <pabeni@redhat.com>
To:     Kees Cook <keescook@chromium.org>
Cc:     Chris von Recklinghausen <crecklin@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>, linux-mm@kvack.org
Date:   Tue, 26 Jun 2018 19:14:47 +0200
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[hopefully fixed the 'mm' recipient]

On Tue, 2018-06-26 at 09:54 -0700, Kees Cook wrote:
> On Tue, Jun 26, 2018 at 2:48 AM, Paolo Abeni <pabeni@redhat.com> wrote:
> > With CONFIG_HARDENED_USERCOPY=y, perf shows ~6% of CPU time spent
> > cumulatively in __check_object_size (~4%) and __virt_addr_valid (~2%).
> 
> Are you able to see which network functions are making the
> __check_object_size() calls?

The call-chain is:

__GI___libc_recvfrom                                                   
entry_SYSCALL_64_after_hwframe                                         
do_syscall_64                                                          
__x64_sys_recvfrom                                                     
__sys_recvfrom                                                         
inet_recvmsg                                                           
udp_recvmsg                                                            
__check_object_size

udp_recvmsg() actually calls copy_to_iter() (inlined) and the latters
calls check_copy_size() (again, inlined).

Cheers,

Paolo