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Message-ID: <20250704054824.1580222-1-kuniyu@google.com>
Date: Fri, 4 Jul 2025 05:48:18 +0000
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>,
Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org,
Jason Baron <jbaron@...mai.com>
Subject: [PATCH v1 net] netlink: Fix wraparounds of sk->sk_rmem_alloc.
Netlink has this pattern in some places
if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
atomic_add(skb->truesize, &sk->sk_rmem_alloc);
, which has the same problem fixed by commit 5a465a0da13e ("udp:
Fix multiple wraparounds of sk->sk_rmem_alloc.").
For example, if we set INT_MAX to SO_RCVBUFFORCE, the condition
is always false as the two operands are of int.
Then, a single socket can eat as many skb as possible until OOM
happens, and we can see multiple wraparounds of sk->sk_rmem_alloc.
Let's fix it by using atomic_add_return() and comparing the two
variables as unsigned int.
Before:
[root@...ora ~]# ss -f netlink
Recv-Q Send-Q Local Address:Port Peer Address:Port
-1668710080 0 rtnl:nl_wraparound/293 *
After:
[root@...ora ~]# ss -f netlink
Recv-Q Send-Q Local Address:Port Peer Address:Port
2147483072 0 rtnl:nl_wraparound/290 *
^
`--- INT_MAX - 576
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Jason Baron <jbaron@...mai.com>
Closes: https://lore.kernel.org/netdev/cover.1750285100.git.jbaron@akamai.com/
Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
---
net/netlink/af_netlink.c | 81 ++++++++++++++++++++++++----------------
1 file changed, 49 insertions(+), 32 deletions(-)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index e8972a857e51..79fbaf7333ce 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -387,7 +387,6 @@ static void netlink_skb_set_owner_r(struct sk_buff *skb, struct sock *sk)
WARN_ON(skb->sk != NULL);
skb->sk = sk;
skb->destructor = netlink_skb_destructor;
- atomic_add(skb->truesize, &sk->sk_rmem_alloc);
sk_mem_charge(sk, skb->truesize);
}
@@ -1212,41 +1211,48 @@ struct sk_buff *netlink_alloc_large_skb(unsigned int size, int broadcast)
int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
long *timeo, struct sock *ssk)
{
+ DECLARE_WAITQUEUE(wait, current);
struct netlink_sock *nlk;
+ unsigned int rmem;
nlk = nlk_sk(sk);
+ rmem = atomic_add_return(skb->truesize, &sk->sk_rmem_alloc);
- if ((atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
- test_bit(NETLINK_S_CONGESTED, &nlk->state))) {
- DECLARE_WAITQUEUE(wait, current);
- if (!*timeo) {
- if (!ssk || netlink_is_kernel(ssk))
- netlink_overrun(sk);
- sock_put(sk);
- kfree_skb(skb);
- return -EAGAIN;
- }
-
- __set_current_state(TASK_INTERRUPTIBLE);
- add_wait_queue(&nlk->wait, &wait);
+ if ((rmem == skb->truesize || rmem < READ_ONCE(sk->sk_rcvbuf)) &&
+ !test_bit(NETLINK_S_CONGESTED, &nlk->state)) {
+ netlink_skb_set_owner_r(skb, sk);
+ return 0;
+ }
- if ((atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
- test_bit(NETLINK_S_CONGESTED, &nlk->state)) &&
- !sock_flag(sk, SOCK_DEAD))
- *timeo = schedule_timeout(*timeo);
+ atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
- __set_current_state(TASK_RUNNING);
- remove_wait_queue(&nlk->wait, &wait);
+ if (!*timeo) {
+ if (!ssk || netlink_is_kernel(ssk))
+ netlink_overrun(sk);
sock_put(sk);
+ kfree_skb(skb);
+ return -EAGAIN;
+ }
- if (signal_pending(current)) {
- kfree_skb(skb);
- return sock_intr_errno(*timeo);
- }
- return 1;
+ __set_current_state(TASK_INTERRUPTIBLE);
+ add_wait_queue(&nlk->wait, &wait);
+ rmem = atomic_read(&sk->sk_rmem_alloc);
+
+ if (((rmem && rmem + skb->truesize > READ_ONCE(sk->sk_rcvbuf)) ||
+ test_bit(NETLINK_S_CONGESTED, &nlk->state)) &&
+ !sock_flag(sk, SOCK_DEAD))
+ *timeo = schedule_timeout(*timeo);
+
+ __set_current_state(TASK_RUNNING);
+ remove_wait_queue(&nlk->wait, &wait);
+ sock_put(sk);
+
+ if (signal_pending(current)) {
+ kfree_skb(skb);
+ return sock_intr_errno(*timeo);
}
- netlink_skb_set_owner_r(skb, sk);
- return 0;
+
+ return 1;
}
static int __netlink_sendskb(struct sock *sk, struct sk_buff *skb)
@@ -1307,6 +1313,7 @@ static int netlink_unicast_kernel(struct sock *sk, struct sk_buff *skb,
ret = -ECONNREFUSED;
if (nlk->netlink_rcv != NULL) {
ret = skb->len;
+ atomic_add(skb->truesize, &sk->sk_rmem_alloc);
netlink_skb_set_owner_r(skb, sk);
NETLINK_CB(skb).sk = ssk;
netlink_deliver_tap_kernel(sk, ssk, skb);
@@ -1383,13 +1390,19 @@ EXPORT_SYMBOL_GPL(netlink_strict_get_check);
static int netlink_broadcast_deliver(struct sock *sk, struct sk_buff *skb)
{
struct netlink_sock *nlk = nlk_sk(sk);
+ unsigned int rmem, rcvbuf;
- if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf &&
+ rmem = atomic_add_return(skb->truesize, &sk->sk_rmem_alloc);
+ rcvbuf = READ_ONCE(sk->sk_rcvbuf);
+
+ if ((rmem != skb->truesize || rmem <= rcvbuf) &&
!test_bit(NETLINK_S_CONGESTED, &nlk->state)) {
netlink_skb_set_owner_r(skb, sk);
__netlink_sendskb(sk, skb);
- return atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1);
+ return rmem > (rcvbuf >> 1);
}
+
+ atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
return -1;
}
@@ -2249,6 +2262,7 @@ static int netlink_dump(struct sock *sk, bool lock_taken)
struct module *module;
int err = -ENOBUFS;
int alloc_min_size;
+ unsigned int rmem;
int alloc_size;
if (!lock_taken)
@@ -2258,9 +2272,6 @@ static int netlink_dump(struct sock *sk, bool lock_taken)
goto errout_skb;
}
- if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
- goto errout_skb;
-
/* NLMSG_GOODSIZE is small to avoid high order allocations being
* required, but it makes sense to _attempt_ a 32KiB allocation
* to reduce number of system calls on dump operations, if user
@@ -2283,6 +2294,12 @@ static int netlink_dump(struct sock *sk, bool lock_taken)
if (!skb)
goto errout_skb;
+ rmem = atomic_add_return(skb->truesize, &sk->sk_rmem_alloc);
+ if (rmem >= READ_ONCE(sk->sk_rcvbuf)) {
+ atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
+ goto errout_skb;
+ }
+
/* Trim skb to allocated size. User is expected to provide buffer as
* large as max(min_dump_alloc, 32KiB (max_recvmsg_len capped at
* netlink_recvmsg())). dump will pack as many smaller messages as
--
2.50.0.727.gbf7dc18ff4-goog
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