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.
Link: https://syzkaller.appspot.com/bug?id=c3bfd8e2450adab3bffe4d80821fbbced600407f [1]
Reported-by: [email protected]
Signed-off-by: Shigeru Yoshida <[email protected]>
---
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 ebc202ffdd8d..bf61ea4b8132 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))
--
2.39.0
On Sun, 26 Feb 2023 03:28:20 +0900 Shigeru Yoshida wrote:
> syzbot reported use-after-free in cfusbl_device_notify() [1]. This
> causes a stack trace like below:
Please repost with the correct fixes tag, presumably:
Fixes: 7ad65bf68d70 ("caif: Add support for CAIF over CDC NCM USB interface")
Please make sure you CC the authors of that commit.
On Mon, Feb 27, 2023 at 06:28:00PM -0800, Jakub Kicinski wrote:
> On Sun, 26 Feb 2023 03:28:20 +0900 Shigeru Yoshida wrote:
> > syzbot reported use-after-free in cfusbl_device_notify() [1]. This
> > causes a stack trace like below:
>
> Please repost with the correct fixes tag, presumably:
>
> Fixes: 7ad65bf68d70 ("caif: Add support for CAIF over CDC NCM USB interface")
>
> Please make sure you CC the authors of that commit.
Sorry, I'll be more careful. I'll prepare v2 patch.
Thanks,
Shigeru
>