On (12/04/18 19:06), Tetsuo Handa wrote:
> On 2018/12/04 11:56, Sergey Senozhatsky wrote:
> > Can we please have something better than 'f'?
>
> OK. To pass 80 column limit, one line increased. ;-)
Ah, so that was the reason :)
[..]
> To close this race, get a snapshot value of printk_time and pa
On 2018/12/04 11:56, Sergey Senozhatsky wrote:
> Can we please have something better than 'f'?
OK. To pass 80 column limit, one line increased. ;-)
< + bool f = syslog_partial ? syslog_time : printk_time;
> + bool time = syslog_partial ? syslog_time : print
On (12/02/18 14:02), Tetsuo Handa wrote:
>
> @@ -1541,11 +1545,13 @@ int do_syslog(int type, char __user *buf, int len,
> int source)
> } else {
> u64 seq = syslog_seq;
> u32 idx = syslog_idx;
> + bool f = syslog_parti
On 2018/12/03 23:14, Petr Mladek wrote:
> Well, IMHO, it does not explain the pagefault above. The copy_to_user()
> could come either from syslog_print() or from syslog_print_all(). They
> both have their own checks that prevent the buf overflow.
>
> The code is tricky but it looks safe now. Is it
On Fri 2018-11-30 23:33:39, Tetsuo Handa wrote:
> and (I can't find the reproducer but) sometimes crashes like
>
> [ 451.988242] BUG: pagefault on kernel address 0x8881337fa000 in
> non-whitelisted uaccess
> [ 451.990465] BUG: unable to handle kernel paging request at 8881337fa000
> [
On Sun 2018-12-02 14:02:28, Tetsuo Handa wrote:
> On 2018/12/02 8:49, kbuild test robot wrote:
> >> kernel/printk/printk.c:2396:5: error: 'printk_time' undeclared (first use
> >> in this function)
> ^~~
> Thanks. printk_time depends on CONFIG_PRINTK=y. Added a dummy definition.
>
On 2018/12/02 8:49, kbuild test robot wrote:
>> kernel/printk/printk.c:2396:5: error: 'printk_time' undeclared (first use in
>> this function)
^~~
Thanks. printk_time depends on CONFIG_PRINTK=y. Added a dummy definition.
>From f903b9fa36159472a207f93e2405e45e3999f650 Mon Sep 17
>From bc9ea8e7878a618fd4490ec287eb691fee144acb Mon Sep 17 00:00:00 2001
From: Tetsuo Handa
Date: Sat, 1 Dec 2018 19:37:42 +0900
Subject: [PATCH] printk: fix printk_time race.
Since printk_time can be toggled via /sys/module/printk/parameters/time ,
it is not safe to assume that output length does
On 2018/11/30 21:30, Petr Mladek wrote:
> I am not fully happy with the solution passing time parameter.
> It is less secure. But it would not break compatibility.
> This particular race might be solved the following way:
>
>
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index
On Fri 2018-11-30 11:26:02, Tetsuo Handa wrote:
> Petr Mladek wrote:
> > See syslog_print_all() and kmsg_dump_get_buffer(). They
> > start with calling msg_print_text() many times to calculate
> > how many messages fit into the given buffer. Then they
> > blindly copy the messages into the buffer.
On (11/29/18 15:19), Petr Mladek wrote:
> This fixes a real problem. It might even avoid a crash.
>
> See syslog_print_all() and kmsg_dump_get_buffer(). They
> start with calling msg_print_text() many times to calculate
> how many messages fit into the given buffer. Then they
> blindly copy the me
Petr Mladek wrote:
> See syslog_print_all() and kmsg_dump_get_buffer(). They
> start with calling msg_print_text() many times to calculate
> how many messages fit into the given buffer. Then they
> blindly copy the messages into the buffer.
>
> Now, the buffer might overflow if the size is calcula
On Sat 2018-11-24 19:50:13, Tetsuo Handa wrote:
> Since /sys/module/printk/parameters/time can change from N to Y between
> "msg_print_text() called print_prefix() with buf == NULL" and
> "msg_print_text() again calls print_prefix() with buf != NULL", it is not
> safe for print_time() to unconditio
Since /sys/module/printk/parameters/time can change from N to Y between
"msg_print_text() called print_prefix() with buf == NULL" and
"msg_print_text() again calls print_prefix() with buf != NULL", it is not
safe for print_time() to unconditionally return 0 if printk_time == false.
Signed-off-by:
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