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[PATCH net v2] net: caif: Fix use-after-free in cfusbl_device_notify()

Shigeru Yoshida posted 1 patch 2 years, 6 months ago 
net/caif/caif_usb.c | 3 +++
1 file changed, 3 insertions(+)
[PATCH net v2] net: caif: Fix use-after-free in cfusbl_device_notify()
Posted by Shigeru Yoshida 2 years, 6 months ago 
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>
Link: https://syzkaller.appspot.com/bug?id=c3bfd8e2450adab3bffe4d80821fbbced600407f [1]
Reported-by: syzbot+b563d33852b893653a9e@syzkaller.appspotmail.com
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
---
 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
Re: [PATCH net v2] net: caif: Fix use-after-free in cfusbl_device_notify()
Posted by patchwork-bot+netdevbpf@kernel.org 2 years, 6 months ago 
Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Thu,  2 Mar 2023 01:39:13 +0900 you wrote:
> 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>
> 
> [...]

Here is the summary with links:
  - [net,v2] net: caif: Fix use-after-free in cfusbl_device_notify()
    https://git.kernel.org/netdev/net/c/9781e98a9711

You are awesome, thank you!
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