[PATCH net-next] net: sched: gred: dynamically allocate tc_gred_qopt_offload
From: Arnd Bergmann <arnd@kernel.org>
Date: 2021-10-19 15:37:50
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Subsystem:
networking [general], tc subsystem, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim, Jiri Pirko, Linus Torvalds
From: Arnd Bergmann <arnd@arndb.de>
The tc_gred_qopt_offload structure has grown too big to be on the
stack for 32-bit architectures after recent changes.
net/sched/sch_gred.c:903:13: error: stack frame size (1180) exceeds limit (1024) in 'gred_destroy' [-Werror,-Wframe-larger-than]
net/sched/sch_gred.c:310:13: error: stack frame size (1212) exceeds limit (1024) in 'gred_offload' [-Werror,-Wframe-larger-than]
Use dynamic allocation to avoid this. Unfortunately, this introduces
a new problem in gred_destroy(), which cannot recover from a failure
to allocate memory, and that may be worse than the potential
stack overflow risk.
Not sure what a better approach might be.
Fixes: 50dc9a8572aa ("net: sched: Merge Qdisc::bstats and Qdisc::cpu_bstats data types")
Fixes: 67c9e6270f30 ("net: sched: Protect Qdisc::bstats with u64_stats")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
net/sched/sch_gred.c | 64 +++++++++++++++++++++++++-------------------
1 file changed, 36 insertions(+), 28 deletions(-)
diff --git a/net/sched/sch_gred.c b/net/sched/sch_gred.c
index 72de08ef8335..59c55c6cf3ea 100644
--- a/net/sched/sch_gred.c
+++ b/net/sched/sch_gred.c@@ -307,46 +307,53 @@ static void gred_reset(struct Qdisc *sch) } } -static void gred_offload(struct Qdisc *sch, enum tc_gred_command command) +static int gred_offload(struct Qdisc *sch, enum tc_gred_command command) { struct gred_sched *table = qdisc_priv(sch); struct net_device *dev = qdisc_dev(sch); - struct tc_gred_qopt_offload opt = { - .command = command, - .handle = sch->handle, - .parent = sch->parent, - }; + struct tc_gred_qopt_offload *opt; if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc) - return; + return -ENXIO; + + opt = kzalloc(sizeof(*opt), GFP_KERNEL); + if (!opt) + return -ENOMEM; + + opt->command = command; + opt->handle = sch->handle; + opt->parent = sch->parent; if (command == TC_GRED_REPLACE) { unsigned int i; - opt.set.grio_on = gred_rio_mode(table); - opt.set.wred_on = gred_wred_mode(table); - opt.set.dp_cnt = table->DPs; - opt.set.dp_def = table->def; + opt->set.grio_on = gred_rio_mode(table); + opt->set.wred_on = gred_wred_mode(table); + opt->set.dp_cnt = table->DPs; + opt->set.dp_def = table->def; for (i = 0; i < table->DPs; i++) { struct gred_sched_data *q = table->tab[i]; if (!q) continue; - opt.set.tab[i].present = true; - opt.set.tab[i].limit = q->limit; - opt.set.tab[i].prio = q->prio; - opt.set.tab[i].min = q->parms.qth_min >> q->parms.Wlog; - opt.set.tab[i].max = q->parms.qth_max >> q->parms.Wlog; - opt.set.tab[i].is_ecn = gred_use_ecn(q); - opt.set.tab[i].is_harddrop = gred_use_harddrop(q); - opt.set.tab[i].probability = q->parms.max_P; - opt.set.tab[i].backlog = &q->backlog; + opt->set.tab[i].present = true; + opt->set.tab[i].limit = q->limit; + opt->set.tab[i].prio = q->prio; + opt->set.tab[i].min = q->parms.qth_min >> q->parms.Wlog; + opt->set.tab[i].max = q->parms.qth_max >> q->parms.Wlog; + opt->set.tab[i].is_ecn = gred_use_ecn(q); + opt->set.tab[i].is_harddrop = gred_use_harddrop(q); + opt->set.tab[i].probability = q->parms.max_P; + opt->set.tab[i].backlog = &q->backlog; } - opt.set.qstats = &sch->qstats; + opt->set.qstats = &sch->qstats; } - dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_GRED, &opt); + dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_GRED, opt); + kfree(opt); + + return 0; } static int gred_offload_dump_stats(struct Qdisc *sch)
@@ -470,8 +477,7 @@ static int gred_change_table_def(struct Qdisc *sch, struct nlattr *dps, } } - gred_offload(sch, TC_GRED_REPLACE); - return 0; + return gred_offload(sch, TC_GRED_REPLACE); } static inline int gred_change_vq(struct Qdisc *sch, int dp,
@@ -719,8 +725,7 @@ static int gred_change(struct Qdisc *sch, struct nlattr *opt, sch_tree_unlock(sch); kfree(prealloc); - gred_offload(sch, TC_GRED_REPLACE); - return 0; + return gred_offload(sch, TC_GRED_REPLACE); err_unlock_free: sch_tree_unlock(sch);
@@ -903,13 +908,16 @@ static int gred_dump(struct Qdisc *sch, struct sk_buff *skb) static void gred_destroy(struct Qdisc *sch) { struct gred_sched *table = qdisc_priv(sch); - int i; + int i, ret; for (i = 0; i < table->DPs; i++) { if (table->tab[i]) gred_destroy_vq(table->tab[i]); } - gred_offload(sch, TC_GRED_DESTROY); + ret = gred_offload(sch, TC_GRED_DESTROY); + + WARN(ret, "%s: failed to disable offload: %pe\n", + __func__, ERR_PTR(ret)); } static struct Qdisc_ops gred_qdisc_ops __read_mostly = {
--
2.29.2