linux-kernel - Re: [PATCH v2 7/9] seccomp: Replace smp_read_barrier_depends() with lockless

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Message-ID: <546F6A05.9080600@gmail.com>
Date:	Fri, 21 Nov 2014 11:36:21 -0500
From:	Pranith Kumar <bobby.prani@...il.com>
To:	Kees Cook <keescook@...omium.org>
CC:	Andy Lutomirski <luto@...capital.net>,
	Will Drewry <wad@...omium.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 7/9] seccomp: Replace smp_read_barrier_depends() with
 lockless_dereference()


On 11/21/2014 11:33 AM, Kees Cook wrote:
> On Fri, Nov 21, 2014 at 7:06 AM, Pranith Kumar <bobby.prani@...il.com> wrote:
>> Recently lockless_dereference() was added which can be used in place of
>> hard-coding smp_read_barrier_depends(). The following PATCH makes the change.
>>
>> Signed-off-by: Pranith Kumar <bobby.prani@...il.com>
>> ---
>>  kernel/seccomp.c | 7 +++----
>>  1 file changed, 3 insertions(+), 4 deletions(-)
> Thanks!
>
> Acked-by: Kees Cook <keescook@...omium.org>
>
> Do you need me to carry this patch in the seccomp tree, or will
> someone else be taking your entire series?
>
> -Kees

Please take this patch individually into your tree. There are discussions about the other patches and I will drop the accepted patches and iterate for the next version.

Thanks!

>> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
>> index 4ef9687..3729b06 100644
>> --- a/kernel/seccomp.c
>> +++ b/kernel/seccomp.c
>> @@ -175,17 +175,16 @@ static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
>>   */
>>  static u32 seccomp_run_filters(struct seccomp_data *sd)
>>  {
>> -       struct seccomp_filter *f = ACCESS_ONCE(current->seccomp.filter);
>>         struct seccomp_data sd_local;
>>         u32 ret = SECCOMP_RET_ALLOW;
>> +       /* Make sure cross-thread synced filter points somewhere sane. */
>> +       struct seccomp_filter *f =
>> +                       lockless_dereference(current->seccomp.filter);
>>
>>         /* Ensure unexpected behavior doesn't result in failing open. */
>>         if (unlikely(WARN_ON(f == NULL)))
>>                 return SECCOMP_RET_KILL;
>>
>> -       /* Make sure cross-thread synced filter points somewhere sane. */
>> -       smp_read_barrier_depends();
>> -
>>         if (!sd) {
>>                 populate_seccomp_data(&sd_local);
>>                 sd = &sd_local;
>> --
>> 1.9.1
>>
>
>

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