From 5ae437ad5a2ed573b1ebb04e0afa70b8869f88dd Mon Sep 17 00:00:00 2001 From: Roman Kapl Date: Mon, 19 Feb 2018 21:32:51 +0100 Subject: [PATCH] net: sched: report if filter is too large to dump 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 Acked-by: Jiri Pirko Acked-by: Cong Wang Signed-off-by: David S. Miller --- net/sched/cls_api.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c index a7dc7271042a..247b7cc20c13 100644 --- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -1397,13 +1397,18 @@ static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb) nla_get_u32(tca[TCA_CHAIN]) != chain->index) continue; if (!tcf_chain_dump(chain, q, parent, skb, cb, - index_start, &index)) + 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; } -- GitLab