From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Wed, 23 Nov 2005 21:37:44 +0000 (-0800)
Subject: [PATCH] Fix crash in unregister_console()
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=e9b15b54d3646108bbd3e054158b402025d3e704;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git

[PATCH] Fix crash in unregister_console()

If unregister_console() is inadvertently called while no consoles are
registered, it will crash trying to dereference NULL pointer.  It is
necessary to fix that because register_console() provides no indication
that it actually registered the console passed in.  In fact, it may well
decide not to register it based on various things...

(akpm: It'd be better to make register_console() return something and fix the
callers.  All 106 of them...)

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/kernel/printk.c b/kernel/printk.c
index ac8a08f36207..5287be83e3e7 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -956,7 +956,7 @@ int unregister_console(struct console *console)
 	if (console_drivers == console) {
 		console_drivers=console->next;
 		res = 0;
-	} else {
+	} else if (console_drivers) {
 		for (a=console_drivers->next, b=console_drivers ;
 		     a; b=a, a=b->next) {
 			if (a == console) {