2022-08-18 09:09:15

by Duoming Zhou

Subject: [PATCH net] nfc: pn533: Fix use-after-free bugs caused by pn532_cmd_timeout

When the pn532 uart device is detaching, the pn532_uart_remove()
is called. But there are no functions in pn532_uart_remove() that
could delete the cmd_timeout timer, which will cause use-after-free
bugs. The process is shown below:

(thread 1) | (thread 2)
| pn532_uart_send_frame
pn532_uart_remove | mod_timer(&pn532->cmd_timeout,...)
... | (wait a time)
kfree(pn532) //FREE | pn532_cmd_timeout
| pn532_uart_send_frame
| pn532->... //USE

This patch adds del_timer_sync() in pn532_uart_remove() in order to
prevent the use-after-free bugs. What's more, the pn53x_unregister_nfc()
is well synchronized, it sets nfc_dev->shutting_down to true and there
are no syscalls could restart the cmd_timeout timer.

Fixes: c656aa4c27b1 ("nfc: pn533: add UART phy driver")
Signed-off-by: Duoming Zhou <[email protected]>
---
drivers/nfc/pn533/uart.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/nfc/pn533/uart.c b/drivers/nfc/pn533/uart.c
index 2caf997f9bc..07596bf5f7d 100644
--- a/drivers/nfc/pn533/uart.c
+++ b/drivers/nfc/pn533/uart.c
@@ -310,6 +310,7 @@ static void pn532_uart_remove(struct serdev_device *serdev)
pn53x_unregister_nfc(pn532->priv);
serdev_device_close(serdev);
pn53x_common_clean(pn532->priv);
+ del_timer_sync(&pn532->cmd_timeout);
kfree_skb(pn532->recv_skb);
kfree(pn532);
}
--
2.17.1

2022-08-22 14:07:03

by patchwork-bot+netdevbpf

Subject: Re: [PATCH net] nfc: pn533: Fix use-after-free bugs caused by pn532_cmd_timeout

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <[email protected]>:

On Thu, 18 Aug 2022 17:06:21 +0800 you wrote:
> When the pn532 uart device is detaching, the pn532_uart_remove()
> is called. But there are no functions in pn532_uart_remove() that
> could delete the cmd_timeout timer, which will cause use-after-free
> bugs. The process is shown below:
>
> (thread 1) | (thread 2)
> | pn532_uart_send_frame
> pn532_uart_remove | mod_timer(&pn532->cmd_timeout,...)
> ... | (wait a time)
> kfree(pn532) //FREE | pn532_cmd_timeout
> | pn532_uart_send_frame
> | pn532->... //USE
>
> [...]

Here is the summary with links:
- [net] nfc: pn533: Fix use-after-free bugs caused by pn532_cmd_timeout
https://git.kernel.org/netdev/net/c/f1e941dbf80a

You are awesome, thank you!
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