linux-kernel - Re: [PATCH v2 1/5] exec: Only compute current once in flush_old

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Date:   Mon, 9 Mar 2020 17:56:28 +0000
From:   Bernd Edlinger <bernd.edlinger@...mail.de>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
CC:     Christian Brauner <christian.brauner@...ntu.com>,
        Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Oleg Nesterov <oleg@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Andrei Vagin <avagin@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Yuyang Du <duyuyang@...il.com>,
        David Hildenbrand <david@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Anshuman Khandual <anshuman.khandual@....com>,
        David Howells <dhowells@...hat.com>,
        James Morris <jamorris@...ux.microsoft.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christian Kellner <christian@...lner.me>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Aleksa Sarai <cyphar@...har.com>,
        "Dmitry V. Levin" <ldv@...linux.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] exec: Only compute current once in flush_old_exec

On 3/9/20 6:34 PM, Eric W. Biederman wrote:
> Bernd Edlinger <bernd.edlinger@...mail.de> writes:
> 
>> On 3/8/20 10:35 PM, Eric W. Biederman wrote:
>>>
>>> Make it clear that current only needs to be computed once in
>>> flush_old_exec.  This may have some efficiency improvements and it
>>> makes the code easier to change.
>>>
>>> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
>>> ---
>>>  fs/exec.c | 9 +++++----
>>>  1 file changed, 5 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/fs/exec.c b/fs/exec.c
>>> index db17be51b112..c3f34791f2f0 100644
>>> --- a/fs/exec.c
>>> +++ b/fs/exec.c
>>> @@ -1260,13 +1260,14 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
>>>   */
>>>  int flush_old_exec(struct linux_binprm * bprm)
>>>  {
>>> +	struct task_struct *me = current;
>>>  	int retval;
>>>  
>>>  	/*
>>>  	 * Make sure we have a private signal table and that
>>>  	 * we are unassociated from the previous thread group.
>>>  	 */
>>> -	retval = de_thread(current);
>>> +	retval = de_thread(me);
>>>  	if (retval)
>>>  		goto out;
>>>  
>>> @@ -1294,10 +1295,10 @@ int flush_old_exec(struct linux_binprm * bprm)
>>>  	bprm->mm = NULL;
>>>  
>>>  	set_fs(USER_DS);
>>> -	current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
>>> +	me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
>>>  					PF_NOFREEZE | PF_NO_SETAFFINITY);
>>
>> I wonder if this line should be aligned with the previous?
> 
> In this case I don't think so.  The style used for second line is indent
> with tabs as much as possible to the right.  I haven't changed that.
> 
> Further mixing a change in indentation style with just a variable rename
> will make the patch confusing to read because two things have to be
> verified at the same time.
> 
> So while I see why you ask I think this bit needs to stay as is.
> 

Ah, okay, I see.
Thanks for explaining this rule, I was not aware of it,
but I am still new here :)


Thanks
Bernd.