This is a note to let you know that I've just added the patch titled

net: sched: report if filter is too large to dump

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: net-sched-report-if-filter-is-too-large-to-dump.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Tue Mar 6 19:02:12 PST 2018

From: Roman Kapl code@rkapl.cz Date: Mon, 19 Feb 2018 21:32:51 +0100 Subject: net: sched: report if filter is too large to dump

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 @@ -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; }

Patches currently in stable-queue which might be from code@rkapl.cz are

queue-4.14/net-sched-report-if-filter-is-too-large-to-dump.patch