From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Fri, 22 Nov 2013 15:47:26 +0000 (+0100)
Subject: TTY: pmac_zilog, check existence of ports in pmz_console_init()
X-Git-Tag: firefly_0821_release~3679^2~3250
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=fb36b98472a57ce5e9aaa81de2a8d21089210071;p=firefly-linux-kernel-4.4.55.git

TTY: pmac_zilog, check existence of ports in pmz_console_init()

commit dc1dc2f8a5dd863bf2e79f338fc3ae29e99c683a upstream.

When booting a multi-platform m68k kernel on a non-Mac with "console=ttyS0"
on the kernel command line, it crashes with:

Unable to handle kernel NULL pointer dereference at virtual address   (null)
Oops: 00000000
PC: [<0013ad28>] __pmz_startup+0x32/0x2a0
...
Call Trace: [<002c5d3e>] pmz_console_setup+0x64/0xe4

The normal tty driver doesn't crash, because init_pmz() checks
pmz_ports_count again after calling pmz_probe().

In the serial console initialization path, pmz_console_init() doesn't do
this, causing the driver to crash later.

Add a check for pmz_ports_count to fix this.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Finn Thain <fthain@telegraphics.com.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/tty/serial/pmac_zilog.c b/drivers/tty/serial/pmac_zilog.c
index b1785f58b6e3..7735bbdccbc9 100644
--- a/drivers/tty/serial/pmac_zilog.c
+++ b/drivers/tty/serial/pmac_zilog.c
@@ -2051,6 +2051,9 @@ static int __init pmz_console_init(void)
 	/* Probe ports */
 	pmz_probe();
 
+	if (pmz_ports_count == 0)
+		return -ENODEV;
+
 	/* TODO: Autoprobe console based on OF */
 	/* pmz_console.index = i; */
 	register_console(&pmz_console);