[PATCH 5.15 424/917] net, neigh: Fix NTF_EXT_LEARNED in combination with NTF_USE

Greg Kroah-Hartman
2021-11-16T00:41:43Z

From: Daniel Borkmann <daniel@iogearbox.net>

[ Upstream commit e4400bbf5b15750e1b59bf4722d18d99be60c69f ]

The NTF_EXT_LEARNED neigh flag is usually propagated back to user space
upon dump of the neighbor table. However, when used in combination with
NTF_USE flag this is not the case despite exempting the entry from the
garbage collector. This results in inconsistent state since entries are
typically marked in neigh->flags with NTF_EXT_LEARNED, but here they are
not. Fix it by propagating the creation flag to ___neigh_create().

Before fix:

# ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a REACHABLE
[...]

After fix:

# ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a extern_learn REACHABLE
[...]

Fixes: 9ce33e46531d ("neighbour: support for NTF_EXT_LEARNED flag")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Roopa Prabhu <roopa@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/core/neighbour.c | 26 ++++++++++++++------------
1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 2d5bc3a75faec..8457d5f97022b 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -379,7 +379,7 @@ EXPORT_SYMBOL(neigh_ifdown);

static struct neighbour *neigh_alloc(struct neigh_table *tbl,
struct net_device *dev,
- bool exempt_from_gc)
+ u8 flags, bool exempt_from_gc)
{
struct neighbour *n = NULL;
unsigned long now = jiffies;
@@ -412,6 +412,7 @@ do_alloc:
n->updated = n->used = now;
n->nud_state = NUD_NONE;
n->output = neigh_blackhole;
+ n->flags = flags;
seqlock_init(&n->hh.hh_lock);
n->parms = neigh_parms_clone(&tbl->parms);
timer_setup(&n->timer, neigh_timer_handler, 0);
@@ -575,19 +576,18 @@ struct neighbour *neigh_lookup_nodev(struct neigh_table *tbl, struct net *net,
}
EXPORT_SYMBOL(neigh_lookup_nodev);

-static struct neighbour *___neigh_create(struct neigh_table *tbl,
- const void *pkey,
- struct net_device *dev,
- bool exempt_from_gc, bool want_ref)
+static struct neighbour *
+___neigh_create(struct neigh_table *tbl, const void *pkey,
+ struct net_device *dev, u8 flags,
+ bool exempt_from_gc, bool want_ref)
{
- struct neighbour *n1, *rc, *n = neigh_alloc(tbl, dev, exempt_from_gc);
- u32 hash_val;
- unsigned int key_len = tbl->key_len;
- int error;
+ u32 hash_val, key_len = tbl->key_len;
+ struct neighbour *n1, *rc, *n;
struct neigh_hash_table *nht;
+ int error;

+ n = neigh_alloc(tbl, dev, flags, exempt_from_gc);
trace_neigh_create(tbl, dev, pkey, n, exempt_from_gc);
-
if (!n) {
rc = ERR_PTR(-ENOBUFS);
goto out;
@@ -674,7 +674,7 @@ out_neigh_release:
struct neighbour *__neigh_create(struct neigh_table *tbl, const void *pkey,
struct net_device *dev, bool want_ref)
{
- return ___neigh_create(tbl, pkey, dev, false, want_ref);
+ return ___neigh_create(tbl, pkey, dev, 0, false, want_ref);
}
EXPORT_SYMBOL(__neigh_create);

@@ -1942,7 +1942,9 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh,

exempt_from_gc = ndm->ndm_state & NUD_PERMANENT ||
ndm->ndm_flags & NTF_EXT_LEARNED;
- neigh = ___neigh_create(tbl, dst, dev, exempt_from_gc, true);
+ neigh = ___neigh_create(tbl, dst, dev,
+ ndm->ndm_flags & NTF_EXT_LEARNED,
+ exempt_from_gc, true);
if (IS_ERR(neigh)) {
err = PTR_ERR(neigh);
goto out;
--
2.33.0