From: Shigeru Yoshida syoshida@redhat.com
[ Upstream commit 9781e98a97110f5e76999058368b4be76a788484 ]
syzbot reported use-after-free in cfusbl_device_notify() [1]. This causes a stack trace like below:
BUG: KASAN: use-after-free in cfusbl_device_notify+0x7c9/0x870 net/caif/caif_usb.c:138 Read of size 8 at addr ffff88807ac4e6f0 by task kworker/u4:6/1214
CPU: 0 PID: 1214 Comm: kworker/u4:6 Not tainted 5.19.0-rc3-syzkaller-00146-g92f20ff72066 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: netns cleanup_net Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description.constprop.0.cold+0xeb/0x467 mm/kasan/report.c:313 print_report mm/kasan/report.c:429 [inline] kasan_report.cold+0xf4/0x1c6 mm/kasan/report.c:491 cfusbl_device_notify+0x7c9/0x870 net/caif/caif_usb.c:138 notifier_call_chain+0xb5/0x200 kernel/notifier.c:87 call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:1945 call_netdevice_notifiers_extack net/core/dev.c:1983 [inline] call_netdevice_notifiers net/core/dev.c:1997 [inline] netdev_wait_allrefs_any net/core/dev.c:10227 [inline] netdev_run_todo+0xbc0/0x10f0 net/core/dev.c:10341 default_device_exit_batch+0x44e/0x590 net/core/dev.c:11334 ops_exit_list+0x125/0x170 net/core/net_namespace.c:167 cleanup_net+0x4ea/0xb00 net/core/net_namespace.c:594 process_one_work+0x996/0x1610 kernel/workqueue.c:2289 worker_thread+0x665/0x1080 kernel/workqueue.c:2436 kthread+0x2e9/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302 </TASK>
When unregistering a net device, unregister_netdevice_many_notify() sets the device's reg_state to NETREG_UNREGISTERING, calls notifiers with NETDEV_UNREGISTER, and adds the device to the todo list.
Later on, devices in the todo list are processed by netdev_run_todo(). netdev_run_todo() waits devices' reference count become 1 while rebdoadcasting NETDEV_UNREGISTER notification.
When cfusbl_device_notify() is called with NETDEV_UNREGISTER multiple times, the parent device might be freed. This could cause UAF. Processing NETDEV_UNREGISTER multiple times also causes inbalance of reference count for the module.
This patch fixes the issue by accepting only first NETDEV_UNREGISTER notification.
Fixes: 7ad65bf68d70 ("caif: Add support for CAIF over CDC NCM USB interface") CC: sjur.brandeland@stericsson.com sjur.brandeland@stericsson.com Reported-by: syzbot+b563d33852b893653a9e@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=c3bfd8e2450adab3bffe4d80821fbbced600407... [1] Signed-off-by: Shigeru Yoshida syoshida@redhat.com Link: https://lore.kernel.org/r/20230301163913.391304-1-syoshida@redhat.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/caif/caif_usb.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/net/caif/caif_usb.c b/net/caif/caif_usb.c index 46c62dd1479b8..862226be22868 100644 --- a/net/caif/caif_usb.c +++ b/net/caif/caif_usb.c @@ -134,6 +134,9 @@ static int cfusbl_device_notify(struct notifier_block *me, unsigned long what, struct usb_device *usbdev; int res;
+ if (what == NETDEV_UNREGISTER && dev->reg_state >= NETREG_UNREGISTERED) + return 0; + /* Check whether we have a NCM device, and find its VID/PID. */ if (!(dev->dev.parent && dev->dev.parent->driver && strcmp(dev->dev.parent->driver->name, "cdc_ncm") == 0))