From e8a10089eddba40d4b2080c9d3fc2d2b2488f762 Mon Sep 17 00:00:00 2001 From: Andy Shevchenko Date: Tue, 2 Apr 2024 22:50:29 +0300 Subject: [PATCH] serial: max3100: Update uart_driver_registered on driver removal MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit [ Upstream commit 712a1fcb38dc7cac6da63ee79a88708fbf9c45ec ] The removal of the last MAX3100 device triggers the removal of the driver. However, code doesn't update the respective global variable and after insmod — rmmod — insmod cycle the kernel oopses: max3100 spi-PRP0001:01: max3100_probe: adding port 0 BUG: kernel NULL pointer dereference, address: 0000000000000408 ... RIP: 0010:serial_core_register_port+0xa0/0x840 ... max3100_probe+0x1b6/0x280 [max3100] spi_probe+0x8d/0xb0 Update the actual state so next time UART driver will be registered again. Hugo also noticed, that the error path in the probe also affected by having the variable set, and not cleared. Instead of clearing it move the assignment after the successfull uart_register_driver() call. Fixes: 7831d56b0a35 ("tty: MAX3100") Signed-off-by: Andy Shevchenko Reviewed-by: Hugo Villeneuve Link: https://lore.kernel.org/r/20240402195306.269276-3-andriy.shevchenko@linux.intel.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/max3100.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/max3100.c b/drivers/tty/serial/max3100.c index 45022f2909f0..b3e63b6a402e 100644 --- a/drivers/tty/serial/max3100.c +++ b/drivers/tty/serial/max3100.c @@ -749,13 +749,14 @@ static int max3100_probe(struct spi_device *spi) mutex_lock(&max3100s_lock); if (!uart_driver_registered) { - uart_driver_registered = 1; retval = uart_register_driver(&max3100_uart_driver); if (retval) { printk(KERN_ERR "Couldn't register max3100 uart driver\n"); mutex_unlock(&max3100s_lock); return retval; } + + uart_driver_registered = 1; } for (i = 0; i < MAX_MAX3100; i++) @@ -841,6 +842,7 @@ static void max3100_remove(struct spi_device *spi) } pr_debug("removing max3100 driver\n"); uart_unregister_driver(&max3100_uart_driver); + uart_driver_registered = 0; mutex_unlock(&max3100s_lock); }