From: Nikolay Aleksandrov nikolay@cumulusnetworks.com
commit 90f33bffa382598a32cc82abfeb20adc92d041b6 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/net/nexthop.h | 1 net/ipv4/nexthop.c | 91 +++++++++++++++++++++++++++++++------------------- 2 files changed, 59 insertions(+), 33 deletions(-)
--- 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; --- a/net/ipv4/nexthop.c +++ b/net/ipv4/nexthop.c @@ -64,9 +64,16 @@ static void nexthop_free_mpath(struct ne 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); }
@@ -698,46 +705,53 @@ static void nh_group_rebalance(struct nh 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, @@ -747,6 +761,9 @@ static void remove_nexthop_from_groups(s
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) @@ -760,10 +777,7 @@ static void remove_nexthop_group(struct 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); } }
@@ -1086,6 +1100,7 @@ static struct nexthop *nexthop_create_gr { 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; @@ -1096,12 +1111,21 @@ static struct nexthop *nexthop_create_gr
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; @@ -1133,6 +1157,7 @@ out_no_nh: for (; i >= 0; --i) nexthop_put(nhg->nh_entries[i].nh);
+ kfree(nhg->spare); kfree(nhg); kfree(nh);