| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20220910222300.712668210@linutronix.de>
Date: Sun, 11 Sep 2022 00:27:41 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: John Ogness <john.ogness@...utronix.de>,
Petr Mladek <pmladek@...e.com>,
Sergey Senozhatsky <senozhatsky@...omium.org>,
Steven Rostedt <rostedt@...dmis.org>,
Linus Torvalds <torvalds@...uxfoundation.org>,
Peter Zijlstra <peterz@...radead.org>,
"Paul E. McKenney" <paulmck@...nel.org>,
Daniel Vetter <daniel@...ll.ch>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Helge Deller <deller@....de>,
Jason Wessel <jason.wessel@...driver.com>,
Daniel Thompson <daniel.thompson@...aro.org>
Subject: [patch RFC 06/29] printk: Protect [un]register_console() with a mutex
Unprotected list walks are a brilliant idea. Especially in the context of
hotpluggable consoles.
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
include/linux/console.h | 30 ++++++++++++++++--
kernel/printk/printk.c | 79 ++++++++++++++++++++++++++++++++++++++++--------
2 files changed, 93 insertions(+), 16 deletions(-)
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -157,10 +157,34 @@ struct console {
struct console *next;
};
-/*
- * for_each_console() allows you to iterate on each console
+#ifdef CONFIG_LOCKDEP
+extern void lockdep_assert_console_list_lock_held(void);
+#else
+static inline void lockdep_assert_console_list_lock_held(void) { }
+#endif
+
+extern void console_list_lock(void) __acquires(console_mutex);
+extern void console_list_unlock(void) __releases(console_mutex);
+
+/**
+ * for_each_registered_console() - Iterator over registered consoles
+ * @con: struct console pointer used as loop cursor
+ *
+ * Requires console_list_lock to be held. Can only be invoked from
+ * preemptible context.
+ */
+#define for_each_registered_console(con) \
+ lockdep_assert_console_list_lock_held(); \
+ for (con = console_drivers; con != NULL; con = con->next)
+
+/**
+ * for_each_console() - Iterator over registered consoles
+ * @con: struct console pointer used as loop cursor
+ *
+ * Requires console_lock to be held which guarantees that the
+ * list is immutable.
*/
-#define for_each_console(con) \
+#define for_each_console(con) \
for (con = console_drivers; con != NULL; con = con->next)
extern int console_set_on_cmdline;
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -79,10 +79,14 @@ int oops_in_progress;
EXPORT_SYMBOL(oops_in_progress);
/*
- * console_sem protects the console_drivers list, and also
- * provides serialisation for access to the entire console
- * driver system.
+ * console_sem protects the console_drivers list, and also provides
+ * serialization for access to the entire console driver system.
+ *
+ * console_mutex serializes register/unregister. console_sem has to be
+ * taken for any list manipulation inside the console_mutex locked
+ * section to keep the console BKL machinery happy.
*/
+static DEFINE_MUTEX(console_mutex);
static DEFINE_SEMAPHORE(console_sem);
struct console *console_drivers;
EXPORT_SYMBOL_GPL(console_drivers);
@@ -103,6 +107,12 @@ static int __read_mostly suppress_panic_
static struct lockdep_map console_lock_dep_map = {
.name = "console_lock"
};
+
+void lockdep_assert_console_list_lock_held(void)
+{
+ lockdep_assert_held(&console_mutex);
+}
+
#endif
enum devkmsg_log_bits {
@@ -220,6 +230,26 @@ int devkmsg_sysctl_set_loglvl(struct ctl
}
#endif /* CONFIG_PRINTK && CONFIG_SYSCTL */
+/**
+ * console_list_lock - Lock the console list
+ *
+ * For non-console related list walks, e.g. procfs, sysfs...
+ */
+void console_list_lock(void)
+{
+ mutex_lock(&console_mutex);
+}
+
+/**
+ * console_list_unlock - Unlock the console list
+ *
+ * Counterpart to console_list_lock()
+ */
+void console_list_unlock(void)
+{
+ mutex_unlock(&console_mutex);
+}
+
/*
* Helper macros to handle lockdep when locking/unlocking console_sem. We use
* macros instead of functions so that _RET_IP_ contains useful information.
@@ -2978,17 +3008,21 @@ struct tty_driver *console_device(int *i
void console_stop(struct console *console)
{
__pr_flush(console, 1000, true);
+ console_list_lock();
console_lock();
console->flags &= ~CON_ENABLED;
console_unlock();
+ console_list_unlock();
}
EXPORT_SYMBOL(console_stop);
void console_start(struct console *console)
{
+ console_list_lock();
console_lock();
console->flags |= CON_ENABLED;
console_unlock();
+ console_list_unlock();
__pr_flush(console, 1000, true);
}
EXPORT_SYMBOL(console_start);
@@ -3081,6 +3115,8 @@ static void try_enable_default_console(s
(con->flags & CON_BOOT) ? "boot" : "", \
con->name, con->index, ##__VA_ARGS__)
+static int console_unregister_locked(struct console *console);
+
/*
* The console driver calls this routine during kernel initialization
* to register the console printing procedure with printk() and to
@@ -3107,13 +3143,14 @@ void register_console(struct console *ne
bool realcon_enabled = false;
int err;
- for_each_console(con) {
+ console_list_lock();
+ for_each_registered_console(con) {
if (WARN(con == newcon, "console '%s%d' already registered\n",
con->name, con->index))
- return;
+ goto unlock;
}
- for_each_console(con) {
+ for_each_registered_console(con) {
if (con->flags & CON_BOOT)
bootcon_enabled = true;
else
@@ -3124,7 +3161,7 @@ void register_console(struct console *ne
if (newcon->flags & CON_BOOT && realcon_enabled) {
pr_info("Too late to register bootconsole %s%d\n",
newcon->name, newcon->index);
- return;
+ goto unlock;
}
/*
@@ -3155,7 +3192,7 @@ void register_console(struct console *ne
/* printk() messages are not printed to the Braille console. */
if (err || newcon->flags & CON_BRL)
- return;
+ goto unlock;
/*
* If we have a bootconsole, and are switching to a real console,
@@ -3209,14 +3246,17 @@ void register_console(struct console *ne
if (bootcon_enabled &&
((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
!keep_bootcon) {
- for_each_console(con)
+ for_each_console(con) {
if (con->flags & CON_BOOT)
- unregister_console(con);
+ console_unregister_locked(con);
+ }
}
+unlock:
+ console_list_unlock();
}
EXPORT_SYMBOL(register_console);
-int unregister_console(struct console *console)
+static int console_unregister_locked(struct console *console)
{
struct console *con;
int res;
@@ -3269,6 +3309,16 @@ int unregister_console(struct console *c
return res;
}
+
+int unregister_console(struct console *console)
+{
+ int res;
+
+ console_list_lock();
+ res = console_unregister_locked(console);
+ console_list_unlock();
+ return res;
+}
EXPORT_SYMBOL(unregister_console);
/*
@@ -3320,7 +3370,8 @@ static int __init printk_late_init(void)
struct console *con;
int ret;
- for_each_console(con) {
+ console_list_lock();
+ for_each_registered_console(con) {
if (!(con->flags & CON_BOOT))
continue;
@@ -3337,9 +3388,11 @@ static int __init printk_late_init(void)
*/
pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n",
con->name, con->index);
- unregister_console(con);
+ console_unregister_locked(con);
}
}
+ console_list_unlock();
+
ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL,
console_cpu_notify);
WARN_ON(ret < 0);
Powered by blists - more mailing lists