genetlink: fix counting regression on ctrl_dumpfamily()
authorStanislaw Gruszka <sgruszka@redhat.com>
Wed, 22 Mar 2017 15:08:33 +0000 (16:08 +0100)
committerDavid S. Miller <davem@davemloft.net>
Wed, 22 Mar 2017 22:38:43 +0000 (15:38 -0700)
commit1d2a6a5e4bf2921531071fcff8538623dce74efa
tree45076a17d569a552c96db9f823c2824d7ea4b656
parenta97e50cc4cb67e1e7bff56f6b41cda62ca832336
genetlink: fix counting regression on ctrl_dumpfamily()

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 <xose.vazquez@gmail.com>
Cc: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Johannes Berg <johannes@sipsolutions.net>
Fixes: 2ae0f17df1cd ("genetlink: use idr to track families")
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/netlink/genetlink.c