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serial: core: clear freed pointers on uart_register_driver() failure

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uart_register_driver() leaves drv->state pointing to freed memory when
tty_alloc_driver() fails. If tty_register_driver() fails, drv->tty_driver
also retains a pointer after its reference is dropped.

Drivers that use drv->state as an "already registered" flag can then skip
registration on the next probe and pass the freed state to
uart_add_one_port().

This issue was found with failslab on QEMU's raspi1ap board by
failing registration and binding the PL011 port again.

Clear both pointers on their failure paths, as uart_unregister_driver()
already does.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Fixes: 9e845abfc8 ("serial: fix NULL pointer dereference")
Assisted-by: Claude:claude-fable-5
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Link: https://patch.msgid.link/20260731181844.11330-3-kmehltretter@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Karl Mehltretter 2026-07-31 20:18:41 +02:00 committed by Greg Kroah-Hartman
parent 1a0e4fbce5
commit 61a2fb2555
1 changed files with 2 additions and 0 deletions
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2
drivers/tty/serial/serial_core.c
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@ -2811,8 +2811,10 @@ int uart_register_driver(struct uart_driver *drv)
for (i = 0; i < drv->nr; i++)
tty_port_destroy(&drv->state[i].port);
tty_driver_kref_put(normal);
drv->tty_driver = NULL;
out_kfree:
kfree(drv->state);
drv->state = NULL;
out:
return retval;
}