linux-kernel - Re: [PATCH] staging: lustre: Fix avoid intensive reconnecting for ko2iblnd patch

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Date:   Wed, 17 Jan 2018 00:36:19 +0000
From:   "Dilger, Andreas" <andreas.dilger@...el.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     "Eremin, Dmitry" <dmitry.eremin@...el.com>,
        "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        "Drokin, Oleg" <oleg.drokin@...el.com>,
        "James Simmons" <jsimmons@...radead.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Lustre Development List" <lustre-devel@...ts.lustre.org>
Subject: Re: [PATCH] staging: lustre: Fix avoid intensive reconnecting for
 ko2iblnd patch


> On Jan 16, 2018, at 09:56, Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
> 
> On Tue, Jan 16, 2018 at 03:01:49PM +0000, Eremin, Dmitry wrote:
>> In the original commit 4d99b2581effe115376402e710fbcb1c3c073769
> 
> Please use the documented way to write this:
> 	4d99b2581eff ("staging: lustre: avoid intensive reconnecting for ko2iblnd")
> 

>> was missed one hunk. Added it now to avoid issue with use after free.
> 
> And I do not understand this commit message at all.
> 
>> Signed-off-by: Dmitry Eremin <Dmitry.Eremin@...el.com>
>> ---
>> drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
>> index 2ebc484..a15a625 100644
>> --- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
>> +++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd.c
>> @@ -890,7 +890,8 @@ void kiblnd_destroy_conn(struct kib_conn *conn, bool free_conn)
>> 		atomic_dec(&net->ibn_nconns);
>> 	}
>> 
>> -	kfree(conn);
>> +	if (free_conn)
>> +		kfree(conn);
> 
> This looks really odd, don't you think?

I'm not sure what the objection is here?  There is an argument to this
this function named "free_conn" which determines if the structure should
be freed, or if the network connection is just being torn down and
reconnected.

Cheers, Andreas
--
Andreas Dilger
Lustre Principal Architect
Intel Corporation