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Jakub Lewalskigregkh
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tty: serial: uartlite: register uart driver in init
[ Upstream commit 6bd697b ] When two instances of uart devices are probing, a concurrency race can occur. If one thread calls uart_register_driver function, which first allocates and assigns memory to 'uart_state' member of uart_driver structure, the other instance can bypass uart driver registration and call ulite_assign. This calls uart_add_one_port, which expects the uart driver to be fully initialized. This leads to a kernel panic due to a null pointer dereference: [ 8.143581] BUG: kernel NULL pointer dereference, address: 00000000000002b8 [ 8.156982] #PF: supervisor write access in kernel mode [ 8.156984] #PF: error_code(0x0002) - not-present page [ 8.156986] PGD 0 P4D 0 ... [ 8.180668] RIP: 0010:mutex_lock+0x19/0x30 [ 8.188624] Call Trace: [ 8.188629] ? __die_body.cold+0x1a/0x1f [ 8.195260] ? page_fault_oops+0x15c/0x290 [ 8.209183] ? __irq_resolve_mapping+0x47/0x80 [ 8.209187] ? exc_page_fault+0x64/0x140 [ 8.209190] ? asm_exc_page_fault+0x22/0x30 [ 8.209196] ? mutex_lock+0x19/0x30 [ 8.223116] uart_add_one_port+0x60/0x440 [ 8.223122] ? proc_tty_register_driver+0x43/0x50 [ 8.223126] ? tty_register_driver+0x1ca/0x1e0 [ 8.246250] ulite_probe+0x357/0x4b0 [uartlite] To prevent it, move uart driver registration in to init function. This will ensure that uart_driver is always registered when probe function is called. Signed-off-by: Jakub Lewalski <[email protected]> Signed-off-by: Elodie Decerle <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
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drivers/tty/serial/uartlite.c

Lines changed: 12 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -880,16 +880,6 @@ static int ulite_probe(struct platform_device *pdev)
880880
pm_runtime_set_active(&pdev->dev);
881881
pm_runtime_enable(&pdev->dev);
882882

883-
if (!ulite_uart_driver.state) {
884-
dev_dbg(&pdev->dev, "uartlite: calling uart_register_driver()\n");
885-
ret = uart_register_driver(&ulite_uart_driver);
886-
if (ret < 0) {
887-
dev_err(&pdev->dev, "Failed to register driver\n");
888-
clk_disable_unprepare(pdata->clk);
889-
return ret;
890-
}
891-
}
892-
893883
ret = ulite_assign(&pdev->dev, id, res->start, irq, pdata);
894884

895885
pm_runtime_mark_last_busy(&pdev->dev);
@@ -929,16 +919,25 @@ static struct platform_driver ulite_platform_driver = {
929919

930920
static int __init ulite_init(void)
931921
{
922+
int ret;
923+
924+
pr_debug("uartlite: calling uart_register_driver()\n");
925+
ret = uart_register_driver(&ulite_uart_driver);
926+
if (ret)
927+
return ret;
932928

933929
pr_debug("uartlite: calling platform_driver_register()\n");
934-
return platform_driver_register(&ulite_platform_driver);
930+
ret = platform_driver_register(&ulite_platform_driver);
931+
if (ret)
932+
uart_unregister_driver(&ulite_uart_driver);
933+
934+
return ret;
935935
}
936936

937937
static void __exit ulite_exit(void)
938938
{
939939
platform_driver_unregister(&ulite_platform_driver);
940-
if (ulite_uart_driver.state)
941-
uart_unregister_driver(&ulite_uart_driver);
940+
uart_unregister_driver(&ulite_uart_driver);
942941
}
943942

944943
module_init(ulite_init);

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