linux-kernel - [PATCH 4.14 65/91] serial: pl011: Fix oops on -EPROBE

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Date:   Tue,  1 Sep 2020 17:10:39 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Lukas Wunner <lukas@...ner.de>,
        Aleksey Makarov <amakarov@...vell.com>,
        Peter Hurley <peter@...leysoftware.com>,
        Russell King <linux@...linux.org.uk>,
        Christopher Covington <cov@...eaurora.org>
Subject: [PATCH 4.14 65/91] serial: pl011: Fix oops on -EPROBE_DEFER

From: Lukas Wunner <lukas@...ner.de>

commit 27afac93e3bd7fa89749cf11da5d86ac9cde4dba upstream.

If probing of a pl011 gets deferred until after free_initmem(), an oops
ensues because pl011_console_match() is called which has been freed.

Fix by removing the __init attribute from the function and those it
calls.

Commit 10879ae5f12e ("serial: pl011: add console matching function")
introduced pl011_console_match() not just for early consoles but
regular preferred consoles, such as those added by acpi_parse_spcr().
Regular consoles may be registered after free_initmem() for various
reasons, one being deferred probing, another being dynamic enablement
of serial ports using a DeviceTree overlay.

Thus, pl011_console_match() must not be declared __init and the
functions it calls mustn't either.

Stack trace for posterity:

Unable to handle kernel paging request at virtual address 80c38b58
Internal error: Oops: 8000000d [#1] PREEMPT SMP ARM
PC is at pl011_console_match+0x0/0xfc
LR is at register_console+0x150/0x468
[<80187004>] (register_console)
[<805a8184>] (uart_add_one_port)
[<805b2b68>] (pl011_register_port)
[<805b3ce4>] (pl011_probe)
[<80569214>] (amba_probe)
[<805ca088>] (really_probe)
[<805ca2ec>] (driver_probe_device)
[<805ca5b0>] (__device_attach_driver)
[<805c8060>] (bus_for_each_drv)
[<805c9dfc>] (__device_attach)
[<805ca630>] (device_initial_probe)
[<805c90a8>] (bus_probe_device)
[<805c95a8>] (deferred_probe_work_func)

Fixes: 10879ae5f12e ("serial: pl011: add console matching function")
Signed-off-by: Lukas Wunner <lukas@...ner.de>
Cc: stable@...r.kernel.org # v4.10+
Cc: Aleksey Makarov <amakarov@...vell.com>
Cc: Peter Hurley <peter@...leysoftware.com>
Cc: Russell King <linux@...linux.org.uk>
Cc: Christopher Covington <cov@...eaurora.org>
Link: https://lore.kernel.org/r/f827ff09da55b8c57d316a1b008a137677b58921.1597315557.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/tty/serial/amba-pl011.c |   11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -2272,9 +2272,8 @@ pl011_console_write(struct console *co,
 	clk_disable(uap->clk);
 }
 
-static void __init
-pl011_console_get_options(struct uart_amba_port *uap, int *baud,
-			     int *parity, int *bits)
+static void pl011_console_get_options(struct uart_amba_port *uap, int *baud,
+				      int *parity, int *bits)
 {
 	if (pl011_read(uap, REG_CR) & UART01x_CR_UARTEN) {
 		unsigned int lcr_h, ibrd, fbrd;
@@ -2307,7 +2306,7 @@ pl011_console_get_options(struct uart_am
 	}
 }
 
-static int __init pl011_console_setup(struct console *co, char *options)
+static int pl011_console_setup(struct console *co, char *options)
 {
 	struct uart_amba_port *uap;
 	int baud = 38400;
@@ -2375,8 +2374,8 @@ static int __init pl011_console_setup(st
  *
  *	Returns 0 if console matches; otherwise non-zero to use default matching
  */
-static int __init pl011_console_match(struct console *co, char *name, int idx,
-				      char *options)
+static int pl011_console_match(struct console *co, char *name, int idx,
+			       char *options)
 {
 	unsigned char iotype;
 	resource_size_t addr;