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Subject[PATCH] serial: 8250: Fix serial8250 initialization crash
Date
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);
--
2.7.4
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