From: Arnd Bergmann arnd@arndb.de
commit 0af413bd3e2de73bcf0742ed556be4af83c71964 upstream.
The fl_flow_key structure is around 500 bytes, so having two of them on the stack in one function now exceeds the warning limit after an otherwise correct change:
net/sched/cls_flower.c:298:12: error: stack frame size of 1056 bytes in function 'fl_classify' [-Werror,-Wframe-larger-than=]
I suspect the fl_classify function could be reworked to only have one of them on the stack and modify it in place, but I could not work out how to do that.
As a somewhat hacky workaround, move one of them into an out-of-line function to reduce its scope. This does not necessarily reduce the stack usage of the outer function, but at least the second copy is removed from the stack during most of it and does not add up to whatever is called from there.
I now see 552 bytes of stack usage for fl_classify(), plus 528 bytes for fl_mask_lookup().
Fixes: 58cff782cc55 ("flow_dissector: Parse multiple MPLS Label Stack Entries") Signed-off-by: Arnd Bergmann arnd@arndb.de Acked-by: Cong Wang xiyou.wangcong@gmail.com Acked-by: Guillaume Nault gnault@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sched/cls_flower.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-)
--- a/net/sched/cls_flower.c +++ b/net/sched/cls_flower.c @@ -270,14 +270,16 @@ static struct cls_fl_filter *fl_lookup_r return NULL; }
-static struct cls_fl_filter *fl_lookup(struct fl_flow_mask *mask, - struct fl_flow_key *mkey, - struct fl_flow_key *key) +static noinline_for_stack +struct cls_fl_filter *fl_mask_lookup(struct fl_flow_mask *mask, struct fl_flow_key *key) { + struct fl_flow_key mkey; + + fl_set_masked_key(&mkey, key, mask); if ((mask->flags & TCA_FLOWER_MASK_FLAGS_RANGE)) - return fl_lookup_range(mask, mkey, key); + return fl_lookup_range(mask, &mkey, key);
- return __fl_lookup(mask, mkey); + return __fl_lookup(mask, &mkey); }
static u16 fl_ct_info_to_flower_map[] = { @@ -297,7 +299,6 @@ static int fl_classify(struct sk_buff *s struct tcf_result *res) { struct cls_fl_head *head = rcu_dereference_bh(tp->root); - struct fl_flow_key skb_mkey; struct fl_flow_key skb_key; struct fl_flow_mask *mask; struct cls_fl_filter *f; @@ -317,9 +318,7 @@ static int fl_classify(struct sk_buff *s ARRAY_SIZE(fl_ct_info_to_flower_map)); skb_flow_dissect(skb, &mask->dissector, &skb_key, 0);
- fl_set_masked_key(&skb_mkey, &skb_key, mask); - - f = fl_lookup(mask, &skb_mkey, &skb_key); + f = fl_mask_lookup(mask, &skb_key); if (f && !tc_skip_sw(f->flags)) { *res = f->res; return tcf_exts_exec(skb, &f->exts, res);