Messages in this thread | | | From | Saubhik Mukherjee <> | Subject | Re: [PATCH] tty: serial: owl: Fix data race in owl_uart_remove | Date | Thu, 24 Jun 2021 17:37:38 +0530 |
| |
On 6/23/21 12:46 PM, Johan Hovold wrote: > On Wed, Jun 23, 2021 at 11:06:53AM +0530, Saubhik Mukherjee wrote: >> On 6/17/21 4:52 PM, Greg KH wrote: >>> On Thu, Jun 17, 2021 at 04:34:43PM +0530, Saubhik Mukherjee wrote: >>>> Suppose the driver is registered and a UART port is added. Once an >>>> application opens the port, owl_uart_startup is called which registers >>>> the interrupt handler owl_uart_irq. >>>> >>>> We could have the following race condition: >>>> >>>> When device is removed, owl_uart_remove is called, which calls >>>> uart_remove_one_port, which calls owl_uart_release_port, which writes >>>> NULL to port->membase. At this point parallely, an interrupt could be >>>> handled by owl_uart_irq which reads port->membase. >>>> >>>> This is because it is possible to remove device without closing a port. >>>> Thus, we need to check it and call owl_uart_shutdown in owl_uart_remove. > > No, this makes no sense at all. The port is deregistered and hung up by > uart_remove_one_port() (and the interrupt line is consequently disabled > by the driver) before it is released so this can never happen.
Thanks for the reply. I am not sure I understand. I could not find any interrupt disabling in owl_uart_remove. Could you point out where/how is the interrupt line is disabled before releasing the port?
A related question question was asked in https://lore.kernel.org/linux-serial/YMcpBXd1vtipueQi@kroah.com/.
>>>> Found by Linux Driver Verification project (linuxtesting.org). > > And you clearly did not test this, which you should mention.
This race warning was found by a static analysis tool. The code changes are untested.
| |