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From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Petr Mladek <pmladek@suse.com>
Cc: Dmitry Vyukov <dvyukov@google.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	syzkaller <syzkaller@googlegroups.com>
Subject: Re: [PATCH] printk: Add caller information to printk() output.
Date: Mon, 10 Dec 2018 23:01:39 +0900	[thread overview]
Message-ID: <c5b5d660-d217-35f0-c4f1-7252367934d1@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20181210130930.bas4fozjhe3dc5nu@pathway.suse.cz>

On 2018/12/10 22:09, Petr Mladek wrote:
>> +#ifdef CONFIG_PRINTK_FROM
>> +#define PREFIX_FROM_MAX		16
>> +#define PREFIX_MAX		(32 + PREFIX_FROM_MAX)
>> +#define LOG_LINE_MAX		(1024 - 32)
> 
> This looks suspicious. We either need to limit LOG_LINE_MAX
> by the real PREFIX_MAX (48). Or we must make sure that
> the code is able to handle an eventual overflow.

Reducing LOG_LINE_MAX makes devkmsg_write() to return -EINVAL.
Is such user visible change acceptable?

> BTW: The limit 48 looks right. If I count correctly, the longest
> prefix might be:
> 
>     <2048>[4294967296,xxxxxx][T4294967296]
> 
> 38 = 6+19+13

Theoretical max (based on variable's bit width) is
6 + 20 + 13 + 1 (for space) + 1 (for '\0') = 41.

We allocate 32 for "<2047>[18446744073.709551] ". Thus,
I chose 48 for "<2047>[18446744073.709551][T4294967295] ".


  reply	other threads:[~2018-12-10 14:01 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-24  7:37 [PATCH] printk: Add caller information to printk() output Tetsuo Handa
2018-11-30 15:40 ` Petr Mladek
2018-12-01 14:44   ` Tetsuo Handa
2018-12-02 11:23     ` Tetsuo Handa
2018-12-04  2:02       ` Sergey Senozhatsky
2018-12-04 10:16         ` Tetsuo Handa
2018-12-04 10:38           ` Sergey Senozhatsky
2018-12-04 15:31           ` Petr Mladek
2018-12-03 15:06     ` Petr Mladek
2018-12-03 21:10       ` Tetsuo Handa
2018-12-04 15:27         ` Petr Mladek
2018-12-05 10:42           ` Tetsuo Handa
2018-12-05 11:50             ` Sergey Senozhatsky
2018-12-07  4:58               ` Tetsuo Handa
2018-12-07  5:31                 ` Sergey Senozhatsky
2018-12-10 13:09             ` Petr Mladek
2018-12-10 14:01               ` Tetsuo Handa [this message]
2018-12-11 10:26                 ` Tetsuo Handa
2018-12-12  2:25                   ` Sergey Senozhatsky
2018-12-12  2:29                     ` Sergey Senozhatsky
2018-12-13 12:18                   ` Petr Mladek
2018-12-13 12:42                     ` Sergey Senozhatsky
2018-12-17 14:54                       ` Petr Mladek
2018-12-17 15:40                         ` Sergey Senozhatsky
2018-12-17 21:05                         ` Tetsuo Handa
2018-12-18  8:39                           ` Petr Mladek
2018-12-18  8:58                             ` Sergey Senozhatsky
2019-01-02 16:09                               ` Dmitry Vyukov
2019-01-03 18:27                                 ` Dmitry Vyukov
2019-01-04  7:33                                   ` Fengguang Wu
2019-01-11 19:34                                   ` Kevin Hilman
2019-01-10 11:27                               ` Tetsuo Handa
2018-12-18  8:55                           ` Sergey Senozhatsky
2018-12-18 10:01                             ` Petr Mladek
2018-12-18 10:10                               ` Sergey Senozhatsky
2019-03-21  2:59                           ` Michael Ellerman
2019-03-21 10:20                             ` Petr Mladek
2019-03-22  0:48                               ` Michael Ellerman

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