Re: [PATCH -next 2/3] batman-adv: Use seq_overflow
From: Al Viro <hidden>
Date: 2013-12-11 07:55:35
Also in:
batman, lkml
On Tue, Dec 10, 2013 at 09:12:43PM -0800, Joe Perches wrote:
quoted hunk ↗ jump to hunk
diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c index 2449afa..dfa5d2d 100644 --- a/net/batman-adv/gateway_client.c +++ b/net/batman-adv/gateway_client.c@@ -517,29 +517,28 @@ static int batadv_write_buffer_text(struct batadv_priv *bat_priv, { struct batadv_gw_node *curr_gw; struct batadv_neigh_node *router; - int ret = -1; router = batadv_orig_node_get_router(gw_node->orig_node); if (!router) - goto out; + return -1;
This (as well as the original) means "fail read(2) with -EINVAL", which might or might not be correct behaviour.
curr_gw = batadv_gw_get_selected_gw_node(bat_priv); - ret = seq_printf(seq, "%s %pM (%3i) %pM [%10s]: %u.%u/%u.%u MBit\n", - (curr_gw == gw_node ? "=>" : " "), - gw_node->orig_node->orig, - router->bat_iv.tq_avg, router->addr, - router->if_incoming->net_dev->name, - gw_node->bandwidth_down / 10, - gw_node->bandwidth_down % 10, - gw_node->bandwidth_up / 10, - gw_node->bandwidth_up % 10); + seq_printf(seq, "%s %pM (%3i) %pM [%10s]: %u.%u/%u.%u MBit\n", + (curr_gw == gw_node ? "=>" : " "), + gw_node->orig_node->orig, + router->bat_iv.tq_avg, router->addr, + router->if_incoming->net_dev->name, + gw_node->bandwidth_down / 10, + gw_node->bandwidth_down % 10, + gw_node->bandwidth_up / 10, + gw_node->bandwidth_up % 10); batadv_neigh_node_free_ref(router); if (curr_gw) batadv_gw_node_free_ref(curr_gw); -out: - return ret; + + return seq_overflow(seq);
... and this is utter junk.
This sucker should return 0. Insufficiently large buffer will be handled
by caller, TYVM, if you give that caller a chance to do so. Returning 1
from ->show() is a bug in almost all cases, and definitely so in this one.
Just in case somebody decides that above is worth copying: It Is Not.
Original code is buggy, plain and simple. This one trades the older
bug ("fail with -EINVAL whenever the buffer is too small") with just as buggy
"silently skip an entry entirely whenever the buffer is too small".
Don't Do That.