6.12-stable review patch. If anyone has any objections, please let me know.
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From: John Sperbeck jsperbeck@google.com
commit f0d0277796db613c124206544b6dbe95b520ab6c upstream.
When __netpoll_setup() is called directly, instead of through netpoll_setup(), the np->skb_pool list head isn't initialized. If skb_pool_flush() is later called, then we hit a NULL pointer in skb_queue_purge_reason(). This can be seen with this repro, when CONFIG_NETCONSOLE is enabled as a module:
ip tuntap add mode tap tap0 ip link add name br0 type bridge ip link set dev tap0 master br0 modprobe netconsole netconsole=4444@10.0.0.1/br0,9353@10.0.0.2/ rmmod netconsole
The backtrace is:
BUG: kernel NULL pointer dereference, address: 0000000000000008 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page ... ... ... Call Trace: <TASK> __netpoll_free+0xa5/0xf0 br_netpoll_cleanup+0x43/0x50 [bridge] do_netpoll_cleanup+0x43/0xc0 netconsole_netdev_event+0x1e3/0x300 [netconsole] unregister_netdevice_notifier+0xd9/0x150 cleanup_module+0x45/0x920 [netconsole] __se_sys_delete_module+0x205/0x290 do_syscall_64+0x70/0x150 entry_SYSCALL_64_after_hwframe+0x76/0x7e
Move the skb_pool list setup and initial skb fill into __netpoll_setup().
Fixes: 221a9c1df790 ("net: netpoll: Individualize the skb pool") Signed-off-by: John Sperbeck jsperbeck@google.com Reviewed-by: Breno Leitao leitao@debian.org Link: https://patch.msgid.link/20250114011354.2096812-1-jsperbeck@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/core/netpoll.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
--- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -632,6 +632,8 @@ int __netpoll_setup(struct netpoll *np, const struct net_device_ops *ops; int err;
+ skb_queue_head_init(&np->skb_pool); + if (ndev->priv_flags & IFF_DISABLE_NETPOLL) { np_err(np, "%s doesn't support polling, aborting\n", ndev->name); @@ -667,6 +669,9 @@ int __netpoll_setup(struct netpoll *np, strscpy(np->dev_name, ndev->name, IFNAMSIZ); npinfo->netpoll = np;
+ /* fill up the skb queue */ + refill_skbs(np); + /* last thing to do is link it to the net device structure */ rcu_assign_pointer(ndev->npinfo, npinfo);
@@ -686,8 +691,6 @@ int netpoll_setup(struct netpoll *np) struct in_device *in_dev; int err;
- skb_queue_head_init(&np->skb_pool); - rtnl_lock(); if (np->dev_name[0]) { struct net *net = current->nsproxy->net_ns; @@ -787,9 +790,6 @@ put_noaddr: } }
- /* fill up the skb queue */ - refill_skbs(np); - err = __netpoll_setup(np, ndev); if (err) goto flush;