4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Roman Kapl <code@xxxxxxxx>
[ Upstream commit 5ae437ad5a2ed573b1ebb04e0afa70b8869f88dd ]
So far, if the filter was too large to fit in the allocated skb, the
kernel did not return any error and stopped dumping. Modify the dumper
so that it returns -EMSGSIZE when a filter fails to dump and it is the
first filter in the skb. If we are not first, we will get a next chance
with more room.
I understand this is pretty near to being an API change, but the
original design (silent truncation) can be considered a bug.
Note: The error case can happen pretty easily if you create a filter
with 32 actions and have 4kb pages. Also recent versions of iproute try
to be clever with their buffer allocation size, which in turn leads to
Signed-off-by: Roman Kapl <code@xxxxxxxx>
Acked-by: Jiri Pirko <jiri@xxxxxxxxxxxx>
Acked-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/sched/cls_api.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -871,13 +871,18 @@ static int tc_dump_tfilter(struct sk_buf
if (tca[TCA_CHAIN] &&
nla_get_u32(tca[TCA_CHAIN]) != chain->index)
continue;
- if (!tcf_chain_dump(chain, skb, cb, index_start, &index))
+ if (!tcf_chain_dump(chain, skb, cb, index_start, &index)) {
+ err = -EMSGSIZE;
break;
+ }
}
cb->args[0] = index;
out:
+ /* If we did no progress, the error (EMSGSIZE) is real */
+ if (skb->len == 0 && err)
+ return err;
return skb->len;
}