6.15-stable review patch. If anyone has any objections, please let me know.
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From: Stanislav Fomichev stfomichev@gmail.com
[ Upstream commit d8d85ef0a631df9127f202e6371bb33a0b589952 ]
Syzkaller reports the following issue:
BUG: sleeping function called from invalid context at kernel/locking/mutex.c:578 __mutex_lock+0x106/0xe80 kernel/locking/mutex.c:746 team_change_rx_flags+0x38/0x220 drivers/net/team/team_core.c:1781 dev_change_rx_flags net/core/dev.c:9145 [inline] __dev_set_promiscuity+0x3f8/0x590 net/core/dev.c:9189 netif_set_promiscuity+0x50/0xe0 net/core/dev.c:9201 dev_set_promiscuity+0x126/0x260 net/core/dev_api.c:286 packet_dev_mc net/packet/af_packet.c:3698 [inline] packet_dev_mclist_delete net/packet/af_packet.c:3722 [inline] packet_notifier+0x292/0xa60 net/packet/af_packet.c:4247 notifier_call_chain+0x1b3/0x3e0 kernel/notifier.c:85 call_netdevice_notifiers_extack net/core/dev.c:2214 [inline] call_netdevice_notifiers net/core/dev.c:2228 [inline] unregister_netdevice_many_notify+0x15d8/0x2330 net/core/dev.c:11972 rtnl_delete_link net/core/rtnetlink.c:3522 [inline] rtnl_dellink+0x488/0x710 net/core/rtnetlink.c:3564 rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6955 netlink_rcv_skb+0x219/0x490 net/netlink/af_netlink.c:2534
Calling `PACKET_ADD_MEMBERSHIP` on an ops-locked device can trigger the `NETDEV_UNREGISTER` notifier, which may require disabling promiscuous and/or allmulti mode. Both of these operations require acquiring the netdev instance lock.
Move the call to `packet_dev_mc` outside of the RCU critical section. The `mclist` modifications (add, del, flush, unregister) are protected by the RTNL, not the RCU. The RCU only protects the `sklist` and its associated `sks`. The delayed operation on the `mclist` entry remains within the RTNL.
Reported-by: syzbot+b191b5ccad8d7a986286@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=b191b5ccad8d7a986286 Fixes: ad7c7b2172c3 ("net: hold netdev instance lock during sysfs operations") Signed-off-by: Stanislav Fomichev stfomichev@gmail.com Reviewed-by: Willem de Bruijn willemb@google.com Link: https://patch.msgid.link/20250522031129.3247266-1-stfomichev@gmail.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/packet/af_packet.c | 21 ++++++++++++++++----- net/packet/internal.h | 1 + 2 files changed, 17 insertions(+), 5 deletions(-)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index d4dba06297c33..20be2c47cf419 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -3713,15 +3713,15 @@ static int packet_dev_mc(struct net_device *dev, struct packet_mclist *i, }
static void packet_dev_mclist_delete(struct net_device *dev, - struct packet_mclist **mlp) + struct packet_mclist **mlp, + struct list_head *list) { struct packet_mclist *ml;
while ((ml = *mlp) != NULL) { if (ml->ifindex == dev->ifindex) { - packet_dev_mc(dev, ml, -1); + list_add(&ml->remove_list, list); *mlp = ml->next; - kfree(ml); } else mlp = &ml->next; } @@ -3769,6 +3769,7 @@ static int packet_mc_add(struct sock *sk, struct packet_mreq_max *mreq) memcpy(i->addr, mreq->mr_address, i->alen); memset(i->addr + i->alen, 0, sizeof(i->addr) - i->alen); i->count = 1; + INIT_LIST_HEAD(&i->remove_list); i->next = po->mclist; po->mclist = i; err = packet_dev_mc(dev, i, 1); @@ -4233,9 +4234,11 @@ static int packet_getsockopt(struct socket *sock, int level, int optname, static int packet_notifier(struct notifier_block *this, unsigned long msg, void *ptr) { - struct sock *sk; struct net_device *dev = netdev_notifier_info_to_dev(ptr); struct net *net = dev_net(dev); + struct packet_mclist *ml, *tmp; + LIST_HEAD(mclist); + struct sock *sk;
rcu_read_lock(); sk_for_each_rcu(sk, &net->packet.sklist) { @@ -4244,7 +4247,8 @@ static int packet_notifier(struct notifier_block *this, switch (msg) { case NETDEV_UNREGISTER: if (po->mclist) - packet_dev_mclist_delete(dev, &po->mclist); + packet_dev_mclist_delete(dev, &po->mclist, + &mclist); fallthrough;
case NETDEV_DOWN: @@ -4277,6 +4281,13 @@ static int packet_notifier(struct notifier_block *this, } } rcu_read_unlock(); + + /* packet_dev_mc might grab instance locks so can't run under rcu */ + list_for_each_entry_safe(ml, tmp, &mclist, remove_list) { + packet_dev_mc(dev, ml, -1); + kfree(ml); + } + return NOTIFY_DONE; }
diff --git a/net/packet/internal.h b/net/packet/internal.h index d5d70712007ad..1e743d0316fdd 100644 --- a/net/packet/internal.h +++ b/net/packet/internal.h @@ -11,6 +11,7 @@ struct packet_mclist { unsigned short type; unsigned short alen; unsigned char addr[MAX_ADDR_LEN]; + struct list_head remove_list; };
/* kbdq - kernel block descriptor queue */