[PATCH net-next] net: sched: Fix hw_stats_type setting in pedit loop

[PATCH net-next] net: sched: Fix hw_stats_type setting in pedit loop

[Petr Machata]

In the commit referenced below, hw_stats_type of an entry is set for every
entry that corresponds to a pedit action. However, the assignment is only
done after the entry pointer is bumped, and therefore could overwrite
memory outside of the entries array.

The reason for this positioning may have been that the current entry's
hw_stats_type is already set above, before the action-type dispatch.
However, if there are no more actions, the assignment is wrong. And if
there are, the next round of the for_each_action loop will make the
assignment before the action-type dispatch anyway.

Therefore fix this issue by simply reordering the two lines.

Fixes: 74522e7baae2 ("net: sched: set the hw_stats_type in pedit loop")
Signed-off-by: Petr Machata <petrm@mellanox.com>
---
 net/sched/cls_api.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 259a2e51ef3e..ca46290c5809 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -3613,8 +3613,8 @@ int tc_setup_flow_action(struct flow_action *flow_action,
 				entry->mangle.mask = tcf_pedit_mask(act, k);
 				entry->mangle.val = tcf_pedit_val(act, k);
 				entry->mangle.offset = tcf_pedit_offset(act, k);
-				entry = &flow_action->entries[++j];
 				entry->hw_stats_type = act->hw_stats_type;
+				entry = &flow_action->entries[++j];
 			}
 		} else if (is_tcf_csum(act)) {
 			entry->id = FLOW_ACTION_CSUM;
-- 
2.20.1

Re: [PATCH net-next] net: sched: Fix hw_stats_type setting in pedit loop

[David Miller]

From: Petr Machata <petrm@mellanox.com>
Date: Wed, 18 Mar 2020 19:42:29 +0200

> In the commit referenced below, hw_stats_type of an entry is set for every
> entry that corresponds to a pedit action. However, the assignment is only
> done after the entry pointer is bumped, and therefore could overwrite
> memory outside of the entries array.
> 
> The reason for this positioning may have been that the current entry's
> hw_stats_type is already set above, before the action-type dispatch.
> However, if there are no more actions, the assignment is wrong. And if
> there are, the next round of the for_each_action loop will make the
> assignment before the action-type dispatch anyway.
> 
> Therefore fix this issue by simply reordering the two lines.
> 
> Fixes: 74522e7baae2 ("net: sched: set the hw_stats_type in pedit loop")
> Signed-off-by: Petr Machata <petrm@mellanox.com>

Good catch, applied, thank you.