[PATCH 1/1] ensure we don't use bootconsoles after init has been released

[PATCH 1/1] ensure we don't use bootconsoles after init has been released

[Robin Getz]

From: Robin Getz <rgetz@blackfin.uclinux.org>

This is a followup to the cleanups for earlyprintk patch from Gerd Hoffmann

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=69331af79cf29e26d1231152a172a1a10c2df511

This ensures that a bootconsole is unregistered if it is not replaced. 
The current implementation spews garbage out the bootconsole in this case,
since the bootconsole structure is normally in the init section, and is
freed, but still used.

Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>

---
 linux-2.6.x/kernel/printk.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)


Index: linux-2.6.x/kernel/printk.c
===================================================================
--- linux-2.6.x/kernel/printk.c
+++ linux-2.6.x/kernel/printk.c
@@ -1104,6 +1104,20 @@
 }
 EXPORT_SYMBOL(unregister_console);
 
+static int __init disable_boot_consoles(void)
+{
+	struct console *con;
+
+	for (con = console_drivers; con; con = con->next) {
+		if (con->flags & CON_BOOT) {
+			printk(KERN_INFO "Turn off boot console %s%d\n",
+				con->name, con->index);
+			unregister_console(con);
+		}
+	}
+}
+late_initcall(disable_boot_consoles);
+
 /**
  * tty_write_message - write a message to a certain tty, not just the console.
  * @tty: the destination tty_struct

Re: [PATCH 1/1] ensure we don't use bootconsoles after init has been released

[Mike Frysinger]

On 8/19/07, Robin Getz <rgetz@blackfin.uclinux.org> wrote:
> +static int __init disable_boot_consoles(void)
> +{
> +       struct console *con;
> +
> +       for (con = console_drivers; con; con = con->next) {
> +               if (con->flags & CON_BOOT) {
> +                       printk(KERN_INFO "Turn off boot console %s%d\n",
> +                               con->name, con->index);
> +                       unregister_console(con);
> +               }
> +       }
> +}

erp, no 'return 0;' ... that'll earn you a warning at build time and
maybe random failures depending on the arch ...
-mike

Re: [PATCH 1/1] ensure we don't use bootconsoles after init has been released

[Paul Mundt]

On Sun, Aug 19, 2007 at 11:11:47PM -0400, Mike Frysinger wrote:
> On 8/19/07, Robin Getz <rgetz@blackfin.uclinux.org> wrote:
> > +static int __init disable_boot_consoles(void)
> > +{
> > +       struct console *con;
> > +
> > +       for (con = console_drivers; con; con = con->next) {
> > +               if (con->flags & CON_BOOT) {
> > +                       printk(KERN_INFO "Turn off boot console %s%d\n",
> > +                               con->name, con->index);
> > +                       unregister_console(con);
> > +               }
> > +       }
> > +}
> 
> erp, no 'return 0;' ... that'll earn you a warning at build time and
> maybe random failures depending on the arch ...

Or better yet, complain if unregister_console() fails, and pass the
failure down.

Re: [PATCH 1/1] ensure we don't use bootconsoles after init has been released

[Robin Getz]

From: Robin Getz <rgetz@blackfin.uclinux.org>
 
This is a followup to the cleanups for earlyprintk patch from Gerd Hoffmann
 
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=69331af79cf29e26d1231152a172a1a10c2df511
 
This ensures that a bootconsole is unregistered if it is not replaced.
The current implementation spews garbage out the bootconsole in this case,
since the bootconsole structure is normally in the init section, and is
freed, but still used.
 
Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>
 
---

linux-2.6.x-old/kernel/printk.c |   15 +++++++++++++++
1 file changed, 15 insertions(+)

Index: linux-2.6.x-old/kernel/printk.c
===================================================================
--- linux-2.6.x-old/kernel/printk.c	(revision 3583)
+++ linux-2.6.x-old/kernel/printk.c	(working copy)
@@ -1104,6 +1104,21 @@
 }
 EXPORT_SYMBOL(unregister_console);
 
+static int __init disable_boot_consoles(void)
+{
+	struct console *con;
+
+	for (con = console_drivers; con; con = con->next) {
+		if (con->flags & CON_BOOT) {
+			printk(KERN_INFO "Turn off boot console %s%d\n",
+				con->name, con->index);
+			unregister_console(con);
+		}
+	}
+	return 0;
+}
+late_initcall(disable_boot_consoles);
+
 /**
  * tty_write_message - write a message to a certain tty, not just the console.
  * @tty: the destination tty_struct

Re: [PATCH 1/1] ensure we don't use bootconsoles after init has been released

[Robin Getz]

Try #3...

From: Robin Getz <rgetz@blackfin.uclinux.org>
 
This is a followup to the cleanups for earlyprintk patch from Gerd Hoffmann
 
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=69331af79cf29e26d1231152a172a1a10c2df511
 
This ensures that a bootconsole is unregistered if it is not replaced.
The current implementation spews garbage out the bootconsole in this case,
since the bootconsole structure is normally in the init section, and is
freed, but still used.
 
Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>
CC: Gerd Hoffmann <kraxel@redhat.com>
CC: Paul Mundt <lethal@linux-sh.org>
CC: Mike Frysinger <vapier.adi@gmail.com>
---
 printk.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)


Index: linux-2.6.x/kernel/printk.c
===================================================================
--- linux-2.6.x/kernel/printk.c
+++ linux-2.6.x/kernel/printk.c
@@ -1104,6 +1104,19 @@
 }
 EXPORT_SYMBOL(unregister_console);
 
+static int __init disable_boot_consoles(void)
+{
+	printk(KERN_INFO "here\n");
+
+	if (console_drivers->flags & CON_BOOT) {
+		printk(KERN_INFO "turn off boot console %s%d\n",
+			console_drivers->name, console_drivers->index);
+		return unregister_console(console_drivers);
+	}
+	return 0;
+}
+late_initcall(disable_boot_consoles);
+
 /**
  * tty_write_message - write a message to a certain tty, not just the console.
  * @tty: the destination tty_struct

Re: [PATCH 1/1] ensure we don't use bootconsoles after init has been released

[Gerd Hoffmann]

Robin Getz wrote:
> Try #3...
> 
> From: Robin Getz <rgetz@blackfin.uclinux.org>
> +static int __init disable_boot_consoles(void)
> +{
> +	printk(KERN_INFO "here\n");

leftover debug printk?

cheers,
  Gerd

Re: [PATCH 1/1] ensure we don't use bootconsoles after init has been released

[Robin Getz]

Try #4... (sorry)
 
From: Robin Getz <rgetz@blackfin.uclinux.org>
 
This is a followup to the cleanups for earlyprintk patch from Gerd Hoffmann
 
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=69331af79cf29e26d1231152a172a1a10c2df511
 
This ensures that a bootconsole is unregistered if it is not replaced.
The current implementation spews garbage out the bootconsole in this case,
since the bootconsole structure is normally in the init section, and is
freed, but still used.
 
Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>
CC: Gerd Hoffmann <kraxel@redhat.com>
CC: Paul Mundt <lethal@linux-sh.org>
CC: Mike Frysinger <vapier.adi@gmail.com>
---

 kernel/printk.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

Index: linux-2.6.x/kernel/printk.c
===================================================================
--- linux-2.6.x/kernel/printk.c	(revision 3583)
+++ linux-2.6.x/kernel/printk.c	(working copy)
@@ -1104,6 +1104,17 @@
 }
 EXPORT_SYMBOL(unregister_console);
 
+static int __init disable_boot_consoles(void)
+{
+	if (console_drivers->flags & CON_BOOT) {
+		printk(KERN_INFO "turn off boot console %s%d\n",
+			console_drivers->name, console_drivers->index);
+		return unregister_console(console_drivers);
+	}
+	return 0;
+}
+late_initcall(disable_boot_consoles);
+
 /**
  * tty_write_message - write a message to a certain tty, not just the console.
  * @tty: the destination tty_struct

Re: [PATCH 1/1] ensure we don't use bootconsoles after init has been released

[Gerd Hoffmann]

Robin Getz wrote:
> This ensures that a bootconsole is unregistered if it is not replaced.
> The current implementation spews garbage out the bootconsole in this case,
> since the bootconsole structure is normally in the init section, and is
> freed, but still used.
>  
> Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>
> CC: Gerd Hoffmann <kraxel@redhat.com>

Acked-by: Gerd Hoffmann <kraxel@redhat.com>

cheers,
  Gerd

Re: [PATCH 1/1] ensure we don't use bootconsoles after init has been released

[Paul Mundt]

On Mon, Aug 20, 2007 at 03:22:47PM -0400, Robin Getz wrote:
> Try #4... (sorry)
>  
> From: Robin Getz <rgetz@blackfin.uclinux.org>
>  
> This is a followup to the cleanups for earlyprintk patch from Gerd Hoffmann
>  
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=69331af79cf29e26d1231152a172a1a10c2df511
>  
> This ensures that a bootconsole is unregistered if it is not replaced.
> The current implementation spews garbage out the bootconsole in this case,
> since the bootconsole structure is normally in the init section, and is
> freed, but still used.
>  
> Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>
> CC: Gerd Hoffmann <kraxel@redhat.com>
> CC: Paul Mundt <lethal@linux-sh.org>
> CC: Mike Frysinger <vapier.adi@gmail.com>

Looks better, thanks.

Acked-by: Paul Mundt <lethal@linux-sh.org>

[PATCH 1/1] fix - ensure we don't use bootconsoles after init has been released

[Robin Getz]

From: Robin Getz <rgetz@blackfin.uclinux.org>

Gerd Hoffmann pointed out that my patch from yesterday can lead 
to a null pointer dereference if the kernel is booted with no
console, and no earlyprintk defined. This fixes that issue.

 printk.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>

---

Index: linux-2.6.x/kernel/printk.c
===================================================================
--- linux-2.6.x/kernel/printk.c	
+++ linux-2.6.x/kernel/printk.c
@@ -1106,10 +1106,12 @@
 
 static int __init disable_boot_consoles(void)
 {
-	if (console_drivers->flags & CON_BOOT) {
-		printk(KERN_INFO "turn off boot console %s%d\n",
-			console_drivers->name, console_drivers->index);
-		return unregister_console(console_drivers);
+	if (console_drivers != NULL) {
+		if (console_drivers->flags & CON_BOOT) {
+			printk(KERN_INFO "turn off boot console %s%d\n",
+				console_drivers->name, console_drivers->index);
+			return unregister_console(console_drivers);
+		}
 	}
 	return 0;
 }