lkml.org 
[lkml]   [2019]   [Apr]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[RFC][PATCH 2/2] printk: take console_sem when accessing console drivers list
Date
We need to take console_sem lock when we iterate console
drivers list. Otherwise, another CPU can concurrently
modify console drivers list or console drivers.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
kernel/printk/printk.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index b0e361ca1bea..c2bccf58d03e 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2674,12 +2674,17 @@ void register_console(struct console *newcon)
struct console_cmdline *c;
static bool has_preferred;

- if (console_drivers)
- for_each_console(bcon)
- if (WARN(bcon == newcon,
- "console '%s%d' already registered\n",
- bcon->name, bcon->index))
- return;
+ console_lock();
+ if (console_drivers) {
+ for_each_console(bcon) {
+ if (bcon != newcon)
+ continue;
+ WARN(1, "console '%s%d' already registered\n",
+ bcon->name, bcon->index);
+ console_unlock();
+ return;
+ }
+ }

/*
* before we register a new CON_BOOT console, make sure we don't
@@ -2691,6 +2696,7 @@ void register_console(struct console *newcon)
if (!(bcon->flags & CON_BOOT)) {
pr_info("Too late to register bootconsole %s%d\n",
newcon->name, newcon->index);
+ console_unlock();
return;
}
}
@@ -2701,6 +2707,7 @@ void register_console(struct console *newcon)

if (!has_preferred || bcon || !console_drivers)
has_preferred = preferred_console >= 0;
+ console_unlock();

/*
* See if we want to use this console driver. If we
--
2.21.0
\
 
 \ /
  Last update: 2019-04-23 08:26    [W:0.103 / U:0.396 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site