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neighbour: Annotate neigh_table.phash_buckets and pneigh_entry.next with __rcu.

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The next patch will free pneigh_entry with call_rcu().

Then, we need to annotate neigh_table.phash_buckets[] and
pneigh_entry.next with __rcu.

To make the next patch cleaner, let's annotate the fields in advance.

Currently, all accesses to the fields are under the neigh table lock,
so rcu_dereference_protected() is used with 1 for now, but most of them
(except in pneigh_delete() and pneigh_ifdown_and_unlock()) will be
replaced with rcu_dereference() and rcu_dereference_check().

Note that pneigh_ifdown_and_unlock() changes pneigh_entry.next to a
local list, which is illegal because the RCU iterator could be moved
to another list.  This part will be fixed in the next patch.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-7-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima
2025-07-16 22:08:11 +00:00
committed by Jakub Kicinski
parent e804bd83c1
commit d63382aea7
2 changed files with 33 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
include/net/neighbour.h
View File

@@ -176,7 +176,7 @@ struct neigh_ops {
};
struct pneigh_entry {
struct pneigh_entry *next;
struct pneigh_entry __rcu *next;
possible_net_t net;
struct net_device *dev;
netdevice_tracker dev_tracker;
@@ -236,7 +236,7 @@ struct neigh_table {
unsigned long last_rand;
struct neigh_statistics __percpu *stats;
struct neigh_hash_table __rcu *nht;
struct pneigh_entry **phash_buckets;
struct pneigh_entry __rcu **phash_buckets;
};
static inline int neigh_parms_family(struct neigh_parms *p)

52
net/core/neighbour.c
View File

@@ -731,7 +731,8 @@ static struct pneigh_entry *__pneigh_lookup_1(struct pneigh_entry *n,
net_eq(pneigh_net(n), net) &&
(n->dev == dev || !n->dev))
return n;
n = n->next;
n = rcu_dereference_protected(n->next, 1);
}
return NULL;
}
@@ -742,7 +743,7 @@ struct pneigh_entry *__pneigh_lookup(struct neigh_table *tbl,
unsigned int key_len = tbl->key_len;
u32 hash_val = pneigh_hash(pkey, key_len);
return __pneigh_lookup_1(tbl->phash_buckets[hash_val],
return __pneigh_lookup_1(rcu_dereference_protected(tbl->phash_buckets[hash_val], 1),
net, pkey, key_len, dev);
}
EXPORT_SYMBOL_GPL(__pneigh_lookup);
@@ -759,7 +760,7 @@ struct pneigh_entry *pneigh_lookup(struct neigh_table *tbl,
hash_val = pneigh_hash(pkey, key_len);
read_lock_bh(&tbl->lock);
n = __pneigh_lookup_1(tbl->phash_buckets[hash_val],
n = __pneigh_lookup_1(rcu_dereference_protected(tbl->phash_buckets[hash_val], 1),
net, pkey, key_len, dev);
read_unlock_bh(&tbl->lock);
@@ -778,7 +779,7 @@ struct pneigh_entry *pneigh_create(struct neigh_table *tbl,
ASSERT_RTNL();
read_lock_bh(&tbl->lock);
n = __pneigh_lookup_1(tbl->phash_buckets[hash_val],
n = __pneigh_lookup_1(rcu_dereference_protected(tbl->phash_buckets[hash_val], 1),
net, pkey, key_len, dev);
read_unlock_bh(&tbl->lock);
@@ -803,7 +804,7 @@ struct pneigh_entry *pneigh_create(struct neigh_table *tbl,
write_lock_bh(&tbl->lock);
n->next = tbl->phash_buckets[hash_val];
tbl->phash_buckets[hash_val] = n;
rcu_assign_pointer(tbl->phash_buckets[hash_val], n);
write_unlock_bh(&tbl->lock);
out:
return n;
@@ -812,16 +813,20 @@ struct pneigh_entry *pneigh_create(struct neigh_table *tbl,
int pneigh_delete(struct neigh_table *tbl, struct net *net, const void *pkey,
struct net_device *dev)
{
struct pneigh_entry *n, **np;
unsigned int key_len = tbl->key_len;
u32 hash_val = pneigh_hash(pkey, key_len);
struct pneigh_entry *n, __rcu **np;
unsigned int key_len;
u32 hash_val;
key_len = tbl->key_len;
hash_val = pneigh_hash(pkey, key_len);
write_lock_bh(&tbl->lock);
for (np = &tbl->phash_buckets[hash_val]; (n = *np) != NULL;
for (np = &tbl->phash_buckets[hash_val];
(n = rcu_dereference_protected(*np, 1)) != NULL;
np = &n->next) {
if (!memcmp(n->key, pkey, key_len) && n->dev == dev &&
net_eq(pneigh_net(n), net)) {
*np = n->next;
rcu_assign_pointer(*np, n->next);
write_unlock_bh(&tbl->lock);
if (tbl->pdestructor)
tbl->pdestructor(n);
@@ -838,17 +843,17 @@ static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
struct net_device *dev,
bool skip_perm)
{
struct pneigh_entry *n, **np, *freelist = NULL;
struct pneigh_entry *n, __rcu **np, *freelist = NULL;
u32 h;
for (h = 0; h <= PNEIGH_HASHMASK; h++) {
np = &tbl->phash_buckets[h];
while ((n = *np) != NULL) {
while ((n = rcu_dereference_protected(*np, 1)) != NULL) {
if (skip_perm && n->permanent)
goto skip;
if (!dev || n->dev == dev) {
*np = n->next;
n->next = freelist;
rcu_assign_pointer(*np, n->next);
rcu_assign_pointer(n->next, freelist);
freelist = n;
continue;
}
@@ -858,7 +863,7 @@ static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
}
write_unlock_bh(&tbl->lock);
while ((n = freelist)) {
freelist = n->next;
freelist = rcu_dereference_protected(n->next, 1);
n->next = NULL;
if (tbl->pdestructor)
tbl->pdestructor(n);
@@ -2794,7 +2799,9 @@ static int pneigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
for (h = s_h; h <= PNEIGH_HASHMASK; h++) {
if (h > s_h)
s_idx = 0;
for (n = tbl->phash_buckets[h], idx = 0; n; n = n->next) {
for (n = rcu_dereference_protected(tbl->phash_buckets[h], 1), idx = 0;
n;
n = rcu_dereference_protected(n->next, 1)) {
if (idx < s_idx || pneigh_net(n) != net)
goto next;
if (neigh_ifindex_filtered(n->dev, filter->dev_idx) ||
@@ -3288,9 +3295,10 @@ static struct pneigh_entry *pneigh_get_first(struct seq_file *seq)
state->flags |= NEIGH_SEQ_IS_PNEIGH;
for (bucket = 0; bucket <= PNEIGH_HASHMASK; bucket++) {
pn = tbl->phash_buckets[bucket];
pn = rcu_dereference_protected(tbl->phash_buckets[bucket], 1);
while (pn && !net_eq(pneigh_net(pn), net))
pn = pn->next;
pn = rcu_dereference_protected(pn->next, 1);
if (pn)
break;
}
@@ -3308,15 +3316,17 @@ static struct pneigh_entry *pneigh_get_next(struct seq_file *seq,
struct neigh_table *tbl = state->tbl;
do {
pn = pn->next;
pn = rcu_dereference_protected(pn->next, 1);
} while (pn && !net_eq(pneigh_net(pn), net));
while (!pn) {
if (++state->bucket > PNEIGH_HASHMASK)
break;
pn = tbl->phash_buckets[state->bucket];
pn = rcu_dereference_protected(tbl->phash_buckets[state->bucket], 1);
while (pn && !net_eq(pneigh_net(pn), net))
pn = pn->next;
pn = rcu_dereference_protected(pn->next, 1);
if (pn)
break;
}