From: Andy Shevchenko andriy.shevchenko@linux.intel.com
stable inclusion from stable-v6.6.33 commit e8a10089eddba40d4b2080c9d3fc2d2b2488f762 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IAD6H2
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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[ 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 andriy.shevchenko@linux.intel.com Reviewed-by: Hugo Villeneuve hvilleneuve@dimonoff.com Link: https://lore.kernel.org/r/20240402195306.269276-3-andriy.shevchenko@linux.in... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Wang Hai wanghai38@huawei.com --- 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); }