diff mbox series

[1/2] printk: Check valid console index for preferred console

Message ID 20231012064300.50221-1-tony@atomide.com
State New
Headers
Series [1/2] printk: Check valid console index for preferred console |

Commit Message

Tony Lindgren Oct. 12, 2023, 6:42 a.m. UTC 
  Let's check for valid console index values for preferred console to avoid
bogus console index numbers from kernel command line.

Let's also return an error for negative index numbers for the preferred
console. Unlike for device drivers, a negative index is not valid for the
preferred console.

Let's also constify idx while at it.

Signed-off-by: Tony Lindgren <tony@atomide.com>
---

Changes since v2:

- Fix a mismerge for const char *name while changing the patch
  order as noted by Jiri

- Clarify patch description and code comments for struct console
  negative index usage as noted by Petr

Changes since v1:

- Use const short idx and return an error on negative values

---
 include/linux/console.h |  2 +-
 kernel/printk/printk.c  | 12 ++++++++++--
 2 files changed, 11 insertions(+), 3 deletions(-)

Comments

Greg KH Oct. 16, 2023, 6:45 p.m. UTC | #1 
On Thu, Oct 12, 2023 at 09:42:56AM +0300, Tony Lindgren wrote:
> Let's check for valid console index values for preferred console to avoid
> bogus console index numbers from kernel command line.
> 
> Let's also return an error for negative index numbers for the preferred
> console. Unlike for device drivers, a negative index is not valid for the
> preferred console.
> 
> Let's also constify idx while at it.
> 
> Signed-off-by: Tony Lindgren <tony@atomide.com>

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Greg KH Oct. 16, 2023, 6:45 p.m. UTC | #2 
On Mon, Oct 16, 2023 at 08:45:00PM +0200, Greg Kroah-Hartman wrote:
> On Thu, Oct 12, 2023 at 09:42:56AM +0300, Tony Lindgren wrote:
> > Let's check for valid console index values for preferred console to avoid
> > bogus console index numbers from kernel command line.
> > 
> > Let's also return an error for negative index numbers for the preferred
> > console. Unlike for device drivers, a negative index is not valid for the
> > preferred console.
> > 
> > Let's also constify idx while at it.
> > 
> > Signed-off-by: Tony Lindgren <tony@atomide.com>
> 
> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Oops, you want these to go through my tree, I'll take them now...
Petr Mladek Oct. 19, 2023, 1:25 p.m. UTC | #3 
On Thu 2023-10-12 09:42:56, Tony Lindgren wrote:
> Let's check for valid console index values for preferred console to avoid
> bogus console index numbers from kernel command line.
> 
> Let's also return an error for negative index numbers for the preferred
> console. Unlike for device drivers, a negative index is not valid for the
> preferred console.
> 
> Let's also constify idx while at it.
> 
> Signed-off-by: Tony Lindgren <tony@atomide.com>

Makes sense:

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr
diff mbox series

Patch

diff --git a/include/linux/console.h b/include/linux/console.h
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -340,7 +340,7 @@  enum con_flush_mode {
 	CONSOLE_REPLAY_ALL,
 };
 
-extern int add_preferred_console(char *name, int idx, char *options);
+extern int add_preferred_console(char *name, const short idx, char *options);
 extern void console_force_preferred_locked(struct console *con);
 extern void register_console(struct console *);
 extern int unregister_console(struct console *);
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2404,12 +2404,20 @@  static void set_user_specified(struct console_cmdline *c, bool user_specified)
 	console_set_on_cmdline = 1;
 }
 
-static int __add_preferred_console(char *name, int idx, char *options,
+static int __add_preferred_console(char *name, const short idx, char *options,
 				   char *brl_options, bool user_specified)
 {
 	struct console_cmdline *c;
 	int i;
 
+	/*
+	 * We use a signed short index for struct console for device drivers to
+	 * indicate a not yet assigned index or port. However, a negative index
+	 * value is not valid for preferred console.
+	 */
+	if (idx < 0)
+		return -EINVAL;
+
 	/*
 	 *	See if this tty is not yet registered, and
 	 *	if we have a slot free.
@@ -2513,7 +2521,7 @@  __setup("console=", console_setup);
  * commonly to provide a default console (ie from PROM variables) when
  * the user has not supplied one.
  */
-int add_preferred_console(char *name, int idx, char *options)
+int add_preferred_console(char *name, const short idx, char *options)
 {
 	return __add_preferred_console(name, idx, options, NULL, false);
 }