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SubjectRe: [PATCH] serial: 8250: Fix serial8250 initialization crash
Date
On 17/01/19 10:00 PM, zhe.he@windriver.com wrote:
> From: He Zhe <zhe.he@windriver.com>
>
> The initialization code of interrupt backoff work might reference NULL
> pointer and cause the following crash, if no port was found.
>
> [ 10.017727] CPU 0 Unable to handle kernel paging request at virtual address 000001b0, epc == 807088e0, ra == 8070863c
> ---- snip ----
> [ 11.704470] [<807088e0>] serial8250_register_8250_port+0x318/0x4ac
> [ 11.747251] [<80708d74>] serial8250_probe+0x148/0x1c0
> [ 11.789301] [<80728450>] platform_drv_probe+0x40/0x94
> [ 11.830515] [<807264f8>] really_probe+0xf8/0x318
> [ 11.870876] [<80726b7c>] __driver_attach+0x110/0x12c
> [ 11.910960] [<80724374>] bus_for_each_dev+0x78/0xcc
> [ 11.951134] [<80725958>] bus_add_driver+0x200/0x234
> [ 11.989756] [<807273d8>] driver_register+0x84/0x148
> [ 12.029832] [<80d72f84>] serial8250_init+0x138/0x198
> [ 12.070447] [<80100e6c>] do_one_initcall+0x5c/0x2a0
> [ 12.110104] [<80d3a208>] kernel_init_freeable+0x370/0x484
> [ 12.150722] [<80a49420>] kernel_init+0x10/0xf8
> [ 12.191517] [<8010756c>] ret_from_kernel_thread+0x14/0x1c
>
> This patch makes sure the initialization code can be reached only if a port
> is found.
>
> Fixes: commit 6d7f677a2afa ("serial: 8250: Rate limit serial port rx interrupts during input overruns")
> Signed-off-by: He Zhe <zhe.he@windriver.com>
> ---
> drivers/tty/serial/8250/8250_core.c | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
> index 189ab12..e441221 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -1070,15 +1070,16 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
>
> ret = 0;
> }
> - }
>
> - /* Initialise interrupt backoff work if required */
> - if (up->overrun_backoff_time_ms > 0) {
> - uart->overrun_backoff_time_ms = up->overrun_backoff_time_ms;
> - INIT_DELAYED_WORK(&uart->overrun_backoff,
> - serial_8250_overrun_backoff_work);
> - } else {
> - uart->overrun_backoff_time_ms = 0;
> + /* Initialise interrupt backoff work if required */
> + if (up->overrun_backoff_time_ms > 0) {
> + uart->overrun_backoff_time_ms =
> + up->overrun_backoff_time_ms;
> + INIT_DELAYED_WORK(&uart->overrun_backoff,
> + serial_8250_overrun_backoff_work);
> + } else {
> + uart->overrun_backoff_time_ms = 0;
> + }
> }
>
> mutex_unlock(&serial_mutex);
>

Reviewed-by: Darwin Dingel <darwin.dingel@alliedtelesis.co.nz>

I presume this is the same issue reported here:

https://www.spinics.net/lists/linux-serial/msg33114.html
https://lkml.org/lkml/2018/12/22/171



Thanks!
Regards,

Darwin

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