4.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Roman Kapl code@rkapl.cz
[ 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@rkapl.cz Acked-by: Jiri Pirko jiri@mellanox.com Acked-by: Cong Wang xiyou.wangcong@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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 @@ -1054,13 +1054,18 @@ static int tc_dump_tfilter(struct sk_buf 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; }