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authorNikolay Aleksandrov <nikolay@cumulusnetworks.com>2020-05-26 12:56:15 -0600
committerDavid S. Miller <davem@davemloft.net>2020-05-26 16:06:06 -0700
commit90f33bffa382598a32cc82abfeb20adc92d041b6 (patch)
tree0dfe49406024d9c4bbc3ad76c5c2d8a6527bd65f
parentac21753a5c2c9a6a2019997481a2ac12bbde48c8 (diff)
nexthops: don't modify published nexthop groups
We must avoid modifying published nexthop groups while they might be in use, otherwise we might see NULL ptr dereferences. In order to do that we allocate 2 nexthoup group structures upon nexthop creation and swap between them when we have to delete an entry. The reason is that we can't fail nexthop group removal, so we can't handle allocation failure thus we move the extra allocation on creation where we can safely fail and return ENOMEM. Fixes: 430a049190de ("nexthop: Add support for nexthop groups") Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com> Signed-off-by: David Ahern <dsahern@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/net/nexthop.h1
-rw-r--r--net/ipv4/nexthop.c91
2 files changed, 59 insertions, 33 deletions
diff --git a/include/net/nexthop.h b/include/net/nexthop.h
index c440ccc861fc..8a343519ed7a 100644
--- a/include/net/nexthop.h
+++ b/include/net/nexthop.h
@@ -70,6 +70,7 @@ struct nh_grp_entry {
};
struct nh_group {
+ struct nh_group *spare; /* spare group for removals */
u16 num_nh;
bool mpath;
bool has_v4;
diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
index b4b772f120a7..563f71bcb2d7 100644
--- a/net/ipv4/nexthop.c
+++ b/net/ipv4/nexthop.c
@@ -63,9 +63,16 @@ static void nexthop_free_mpath(struct nexthop *nh)
int i;
nhg = rcu_dereference_raw(nh->nh_grp);
- for (i = 0; i < nhg->num_nh; ++i)
- WARN_ON(nhg->nh_entries[i].nh);
+ for (i = 0; i < nhg->num_nh; ++i) {
+ struct nh_grp_entry *nhge = &nhg->nh_entries[i];
+ WARN_ON(!list_empty(&nhge->nh_list));
+ nexthop_put(nhge->nh);
+ }
+
+ WARN_ON(nhg->spare == nhg);
+
+ kfree(nhg->spare);
kfree(nhg);
}
@@ -697,46 +704,53 @@ static void nh_group_rebalance(struct nh_group *nhg)
static void remove_nh_grp_entry(struct net *net, struct nh_grp_entry *nhge,
struct nl_info *nlinfo)
{
+ struct nh_grp_entry *nhges, *new_nhges;
struct nexthop *nhp = nhge->nh_parent;
struct nexthop *nh = nhge->nh;
- struct nh_grp_entry *nhges;
- struct nh_group *nhg;
- bool found = false;
- int i;
+ struct nh_group *nhg, *newg;
+ int i, j;
WARN_ON(!nh);
- list_del(&nhge->nh_list);
-
nhg = rtnl_dereference(nhp->nh_grp);
- nhges = nhg->nh_entries;
- for (i = 0; i < nhg->num_nh; ++i) {
- if (found) {
- nhges[i-1].nh = nhges[i].nh;
- nhges[i-1].weight = nhges[i].weight;
- list_del(&nhges[i].nh_list);
- list_add(&nhges[i-1].nh_list, &nhges[i-1].nh->grp_list);
- } else if (nhg->nh_entries[i].nh == nh) {
- found = true;
- }
- }
+ newg = nhg->spare;
- if (WARN_ON(!found))
+ /* last entry, keep it visible and remove the parent */
+ if (nhg->num_nh == 1) {
+ remove_nexthop(net, nhp, nlinfo);
return;
+ }
- nhg->num_nh--;
- nhg->nh_entries[nhg->num_nh].nh = NULL;
+ newg->has_v4 = nhg->has_v4;
+ newg->mpath = nhg->mpath;
+ newg->num_nh = nhg->num_nh;
- nh_group_rebalance(nhg);
+ /* copy old entries to new except the one getting removed */
+ nhges = nhg->nh_entries;
+ new_nhges = newg->nh_entries;
+ for (i = 0, j = 0; i < nhg->num_nh; ++i) {
+ /* current nexthop getting removed */
+ if (nhg->nh_entries[i].nh == nh) {
+ newg->num_nh--;
+ continue;
+ }
- nexthop_put(nh);
+ list_del(&nhges[i].nh_list);
+ new_nhges[j].nh_parent = nhges[i].nh_parent;
+ new_nhges[j].nh = nhges[i].nh;
+ new_nhges[j].weight = nhges[i].weight;
+ list_add(&new_nhges[j].nh_list, &new_nhges[j].nh->grp_list);
+ j++;
+ }
+
+ nh_group_rebalance(newg);
+ rcu_assign_pointer(nhp->nh_grp, newg);
+
+ list_del(&nhge->nh_list);
+ nexthop_put(nhge->nh);
if (nlinfo)
nexthop_notify(RTM_NEWNEXTHOP, nhp, nlinfo);
-
- /* if this group has no more entries then remove it */
- if (!nhg->num_nh)
- remove_nexthop(net, nhp, nlinfo);
}
static void remove_nexthop_from_groups(struct net *net, struct nexthop *nh,
@@ -746,6 +760,9 @@ static void remove_nexthop_from_groups(struct net *net, struct nexthop *nh,
list_for_each_entry_safe(nhge, tmp, &nh->grp_list, nh_list)
remove_nh_grp_entry(net, nhge, nlinfo);
+
+ /* make sure all see the newly published array before releasing rtnl */
+ synchronize_rcu();
}
static void remove_nexthop_group(struct nexthop *nh, struct nl_info *nlinfo)
@@ -759,10 +776,7 @@ static void remove_nexthop_group(struct nexthop *nh, struct nl_info *nlinfo)
if (WARN_ON(!nhge->nh))
continue;
- list_del(&nhge->nh_list);
- nexthop_put(nhge->nh);
- nhge->nh = NULL;
- nhg->num_nh--;
+ list_del_init(&nhge->nh_list);
}
}
@@ -1085,6 +1099,7 @@ static struct nexthop *nexthop_create_group(struct net *net,
{
struct nlattr *grps_attr = cfg->nh_grp;
struct nexthop_grp *entry = nla_data(grps_attr);
+ u16 num_nh = nla_len(grps_attr) / sizeof(*entry);
struct nh_group *nhg;
struct nexthop *nh;
int i;
@@ -1095,12 +1110,21 @@ static struct nexthop *nexthop_create_group(struct net *net,
nh->is_group = 1;
- nhg = nexthop_grp_alloc(nla_len(grps_attr) / sizeof(*entry));
+ nhg = nexthop_grp_alloc(num_nh);
if (!nhg) {
kfree(nh);
return ERR_PTR(-ENOMEM);
}
+ /* spare group used for removals */
+ nhg->spare = nexthop_grp_alloc(num_nh);
+ if (!nhg) {
+ kfree(nhg);
+ kfree(nh);
+ return NULL;
+ }
+ nhg->spare->spare = nhg;
+
for (i = 0; i < nhg->num_nh; ++i) {
struct nexthop *nhe;
struct nh_info *nhi;
@@ -1132,6 +1156,7 @@ out_no_nh:
for (; i >= 0; --i)
nexthop_put(nhg->nh_entries[i].nh);
+ kfree(nhg->spare);
kfree(nhg);
kfree(nh);