[PATCH 5.10 26/67] nfc: nfcsim: fix use after free during module unload

Greg Kroah-Hartman
2021-08-02T14:03:00Z

From: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>

commit 5e7b30d24a5b8cb691c173b45b50e3ca0191be19 upstream.

There is a use after free memory corruption during module exit:
- nfcsim_exit()
- nfcsim_device_free(dev0)
- nfc_digital_unregister_device()
This iterates over command queue and frees all commands,
- dev->up = false
- nfcsim_link_shutdown()
- nfcsim_link_recv_wake()
This wakes the sleeping thread nfcsim_link_recv_skb().

- nfcsim_link_recv_skb()
Wake from wait_event_interruptible_timeout(),
call directly the deb->cb callback even though (dev->up == false),
- digital_send_cmd_complete()
Dereference of "struct digital_cmd" cmd which was freed earlier by
nfc_digital_unregister_device().

This causes memory corruption shortly after (with unrelated stack
trace):

nfc nfc0: NFC: nfcsim_recv_wq: Device is down
llcp: nfc_llcp_recv: err -19
nfc nfc1: NFC: nfcsim_recv_wq: Device is down
BUG: unable to handle page fault for address: ffffffffffffffed
Call Trace:
fsnotify+0x54b/0x5c0
__fsnotify_parent+0x1fe/0x300
? vfs_write+0x27c/0x390
vfs_write+0x27c/0x390
ksys_write+0x63/0xe0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae

KASAN report:

BUG: KASAN: use-after-free in digital_send_cmd_complete+0x16/0x50
Write of size 8 at addr ffff88800a05f720 by task kworker/0:2/71
Workqueue: events nfcsim_recv_wq [nfcsim]
Call Trace:
dump_stack_lvl+0x45/0x59
print_address_description.constprop.0+0x21/0x140
? digital_send_cmd_complete+0x16/0x50
? digital_send_cmd_complete+0x16/0x50
kasan_report.cold+0x7f/0x11b
? digital_send_cmd_complete+0x16/0x50
? digital_dep_link_down+0x60/0x60
digital_send_cmd_complete+0x16/0x50
nfcsim_recv_wq+0x38f/0x3d5 [nfcsim]
? nfcsim_in_send_cmd+0x4a/0x4a [nfcsim]
? lock_is_held_type+0x98/0x110
? finish_wait+0x110/0x110
? rcu_read_lock_sched_held+0x9c/0xd0
? rcu_read_lock_bh_held+0xb0/0xb0
? lockdep_hardirqs_on_prepare+0x12e/0x1f0

This flow of calling digital_send_cmd_complete() callback on driver exit
is specific to nfcsim which implements reading and sending work queues.
Since the NFC digital device was unregistered, the callback should not
be called.

Fixes: 204bddcb508f ("NFC: nfcsim: Make use of the Digital layer")
Cc: <stable@vger.kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/nfc/nfcsim.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/nfc/nfcsim.c
+++ b/drivers/nfc/nfcsim.c
@@ -192,8 +192,7 @@ static void nfcsim_recv_wq(struct work_s

if (!IS_ERR(skb))
dev_kfree_skb(skb);
-
- skb = ERR_PTR(-ENODEV);
+ return;
}

dev->cb(dev->nfc_digital_dev, dev->arg, skb);