This is a note to let you know that I've just added the patch titled
net: caif: Fix use-after-free in cfusbl_device_notify()
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-caif-fix-use-after-free-in-cfusbl_device_notify.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit c3440b18719063714668c00d2fa8b05cc07f1e9d
Author: Shigeru Yoshida <syoshida@xxxxxxxxxx>
Date: Thu Mar 2 01:39:13 2023 +0900
net: caif: Fix use-after-free in cfusbl_device_notify()
[ 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@xxxxxxxxxxxxxx <sjur.brandeland@xxxxxxxxxxxxxx>
Reported-by: syzbot+b563d33852b893653a9e@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://syzkaller.appspot.com/bug?id=c3bfd8e2450adab3bffe4d80821fbbced600407f [1]
Signed-off-by: Shigeru Yoshida <syoshida@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230301163913.391304-1-syoshida@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/caif/caif_usb.c b/net/caif/caif_usb.c
index 485dde566c1a9..98c0548c6f947 100644
--- a/net/caif/caif_usb.c
+++ b/net/caif/caif_usb.c
@@ -135,6 +135,9 @@ 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))
