5.4-stable review patch. If anyone has any objections, please let me know.
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From: Kuniyuki Iwashima kuniyu@google.com
[ Upstream commit 706cc36477139c1616a9b2b96610a8bb520b7119 ]
atmarpd is protected by RTNL since commit f3a0592b37b8 ("[ATM]: clip causes unregister hang").
However, it is not enough because to_atmarpd() is called without RTNL, especially clip_neigh_solicit() / neigh_ops->solicit() is unsleepable.
Also, there is no RTNL dependency around atmarpd.
Let's use a private mutex and RCU to protect access to atmarpd in to_atmarpd().
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kuniyuki Iwashima kuniyu@google.com Reviewed-by: Simon Horman horms@kernel.org Link: https://patch.msgid.link/20250704062416.1613927-2-kuniyu@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/atm/clip.c | 44 +++++++++++++++++++++++++++++--------------- 1 file changed, 29 insertions(+), 15 deletions(-)
diff --git a/net/atm/clip.c b/net/atm/clip.c index 294cb9efe3d38..d5363ae5296ad 100644 --- a/net/atm/clip.c +++ b/net/atm/clip.c @@ -45,7 +45,8 @@ #include <net/atmclip.h>
static struct net_device *clip_devs; -static struct atm_vcc *atmarpd; +static struct atm_vcc __rcu *atmarpd; +static DEFINE_MUTEX(atmarpd_lock); static struct timer_list idle_timer; static const struct neigh_ops clip_neigh_ops;
@@ -53,24 +54,35 @@ static int to_atmarpd(enum atmarp_ctrl_type type, int itf, __be32 ip) { struct sock *sk; struct atmarp_ctrl *ctrl; + struct atm_vcc *vcc; struct sk_buff *skb; + int err = 0;
pr_debug("(%d)\n", type); - if (!atmarpd) - return -EUNATCH; + + rcu_read_lock(); + vcc = rcu_dereference(atmarpd); + if (!vcc) { + err = -EUNATCH; + goto unlock; + } skb = alloc_skb(sizeof(struct atmarp_ctrl), GFP_ATOMIC); - if (!skb) - return -ENOMEM; + if (!skb) { + err = -ENOMEM; + goto unlock; + } ctrl = skb_put(skb, sizeof(struct atmarp_ctrl)); ctrl->type = type; ctrl->itf_num = itf; ctrl->ip = ip; - atm_force_charge(atmarpd, skb->truesize); + atm_force_charge(vcc, skb->truesize);
- sk = sk_atm(atmarpd); + sk = sk_atm(vcc); skb_queue_tail(&sk->sk_receive_queue, skb); sk->sk_data_ready(sk); - return 0; +unlock: + rcu_read_unlock(); + return err; }
static void link_vcc(struct clip_vcc *clip_vcc, struct atmarp_entry *entry) @@ -608,10 +620,12 @@ static void atmarpd_close(struct atm_vcc *vcc) { pr_debug("\n");
- rtnl_lock(); - atmarpd = NULL; + mutex_lock(&atmarpd_lock); + RCU_INIT_POINTER(atmarpd, NULL); + mutex_unlock(&atmarpd_lock); + + synchronize_rcu(); skb_queue_purge(&sk_atm(vcc)->sk_receive_queue); - rtnl_unlock();
pr_debug("(done)\n"); module_put(THIS_MODULE); @@ -632,15 +646,15 @@ static struct atm_dev atmarpd_dev = {
static int atm_init_atmarp(struct atm_vcc *vcc) { - rtnl_lock(); + mutex_lock(&atmarpd_lock); if (atmarpd) { - rtnl_unlock(); + mutex_unlock(&atmarpd_lock); return -EADDRINUSE; }
mod_timer(&idle_timer, jiffies + CLIP_CHECK_INTERVAL * HZ);
- atmarpd = vcc; + rcu_assign_pointer(atmarpd, vcc); set_bit(ATM_VF_META, &vcc->flags); set_bit(ATM_VF_READY, &vcc->flags); /* allow replies and avoid getting closed if signaling dies */ @@ -649,7 +663,7 @@ static int atm_init_atmarp(struct atm_vcc *vcc) vcc->push = NULL; vcc->pop = NULL; /* crash */ vcc->push_oam = NULL; /* crash */ - rtnl_unlock(); + mutex_unlock(&atmarpd_lock); return 0; }