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Subject: Re: [PATCH 7/7] sysvipc_find_ipc should increase position index
To:     Vasily Averin <vvs@virtuozzo.com>, linux-kernel@vger.kernel.org
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        NeilBrown <neilb@suse.com>, Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Oberparleiter <oberpar@linux.ibm.com>
References: <b7a20945-e315-8bb0-21e6-3875c14a8494@virtuozzo.com>
From:   Waiman Long <longman@redhat.com>
Organization: Red Hat
Message-ID: <8ed2850e-7cec-ebeb-4e15-21da3715c42a@redhat.com>
Date:   Fri, 24 Jan 2020 11:26:16 -0500
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On 1/24/20 2:03 AM, Vasily Averin wrote:
> if seq_file .next fuction does not change position index,
> read after some lseek can generate unexpected output.
>
> https://bugzilla.kernel.org/show_bug.cgi?id=206283
> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
> ---
>  ipc/util.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/ipc/util.c b/ipc/util.c
> index 915eacb..7a3ab2e 100644
> --- a/ipc/util.c
> +++ b/ipc/util.c
> @@ -764,13 +764,13 @@ static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
>  			total++;
>  	}
>  
> +	*new_pos = pos + 1;
>  	if (total >= ids->in_use)
>  		return NULL;
>  
>  	for (; pos < ipc_mni; pos++) {
>  		ipc = idr_find(&ids->ipcs_idr, pos);
>  		if (ipc != NULL) {
> -			*new_pos = pos + 1;
>  			rcu_read_lock();
>  			ipc_lock_object(ipc);
>  			return ipc;

Acked-by: Waiman Long <longman@redhat.com>