Re: [PATCH 4.11] genetlink: fix counting regression on ctrl_dumpfamily()

[poma]

On 22.03.2017 16:08, Stanislaw Gruszka wrote:
> Commit 2ae0f17df1cd ("genetlink: use idr to track families") replaced
> 
>   if (++n < fams_to_skip)
>   continue;
> into:
> 
>   if (n++ < fams_to_skip)
>   continue;
> 
> This subtle change cause that on retry ctrl_dumpfamily() call we omit
> one family that failed to do ctrl_fill_info() on previous call, because
> cb->args[0] = n number counts also family that failed to do
> ctrl_fill_info().
> 
> Patch fixes the problem and avoid confusion in the future just decrease
> n counter when ctrl_fill_info() fail.
> 
> User visible problem caused by this bug is failure to get access to
> some genetlink family i.e. nl80211. However problem is reproducible
> only if number of registered genetlink families is big enough to
> cause second call of ctrl_dumpfamily().
> 
> Cc: Xose Vazquez Perez 
> Cc: Larry Finger 
> Cc: Johannes Berg 
> Fixes: 2ae0f17df1cd ("genetlink: use idr to track families")
> Signed-off-by: Stanislaw Gruszka 
> ---
> Dave, please also target this for 4.10+ -stable.
> 
>  net/netlink/genetlink.c |4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
> index fb6e10f..92e0981 100644
> --- a/net/netlink/genetlink.c
> +++ b/net/netlink/genetlink.c
> @@ -783,8 +783,10 @@ static int ctrl_dumpfamily(struct sk_buff *skb, struct 
> netlink_callback *cb)
>  
>   if (ctrl_fill_info(rt, NETLINK_CB(cb->skb).portid,
>  cb->nlh->nlmsg_seq, NLM_F_MULTI,
> -skb, CTRL_CMD_NEWFAMILY) < 0)
> +skb, CTRL_CMD_NEWFAMILY) < 0) {
> + n--;
>   break;
> + }
>   }
>  
>   cb->args[0] = n;
> 


Thanks Stanislaw, Larry!

Tested-by: poma 

Ref.
https://bugzilla.redhat.com/show_bug.cgi?id=1422247

Re: [PATCH 4.11] genetlink: fix counting regression on ctrl_dumpfamily()

[David Miller]

From: Stanislaw Gruszka 
Date: Wed, 22 Mar 2017 16:08:33 +0100

> Commit 2ae0f17df1cd ("genetlink: use idr to track families") replaced
> 
>   if (++n < fams_to_skip)
>   continue;
> into:
> 
>   if (n++ < fams_to_skip)
>   continue;
> 
> This subtle change cause that on retry ctrl_dumpfamily() call we omit
> one family that failed to do ctrl_fill_info() on previous call, because
> cb->args[0] = n number counts also family that failed to do
> ctrl_fill_info().
> 
> Patch fixes the problem and avoid confusion in the future just decrease
> n counter when ctrl_fill_info() fail.
> 
> User visible problem caused by this bug is failure to get access to
> some genetlink family i.e. nl80211. However problem is reproducible
> only if number of registered genetlink families is big enough to
> cause second call of ctrl_dumpfamily().
> 
> Cc: Xose Vazquez Perez 
> Cc: Larry Finger 
> Cc: Johannes Berg 
> Fixes: 2ae0f17df1cd ("genetlink: use idr to track families")
> Signed-off-by: Stanislaw Gruszka 

Applied and queued up for -stable, thanks.

Re: [PATCH 4.11] genetlink: fix counting regression on ctrl_dumpfamily()

[Johannes Berg]

On Wed, 2017-03-22 at 16:08 +0100, Stanislaw Gruszka wrote:
> Commit 2ae0f17df1cd ("genetlink: use idr to track families") replaced
> 
>   if (++n < fams_to_skip)
>   continue;
> into:
> 
>   if (n++ < fams_to_skip)
>   continue;

D'oh. I don't know how that ended up in there, tbh.

Acked-by: Johannes Berg 

johannes