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From: Petr Mladek <pmladek@suse.com>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: zhe.he@windriver.com, rostedt@goodmis.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 4/4] printk: Give error on attempt to set log buffer length to over 4G
Date: Tue, 9 Oct 2018 15:05:38 +0200	[thread overview]
Message-ID: <20181009130538.7rtd3du2d7l6m63w@pathway.suse.cz> (raw)
In-Reply-To: <20181008145950.GA1473@tigerII.localdomain>

On Mon 2018-10-08 23:59:50, Sergey Senozhatsky wrote:
> On (10/08/18 15:59), Petr Mladek wrote:
> > I tried this patch with log_buf_len=5G. The kernel did not crash
> > but dmesg shown some mess. There are several 32-bit variables
> > to store the size, for example:
> > 
> > static u32 log_buf_len = __LOG_BUF_LEN;
> > u32 log_buf_len_get(void)
> > static u32 log_first_idx;
> > static u32 log_next_idx;
> > 
> > I guess that the code somewhere does not detect an overflows
> > correctly.
> > 
> > I am not motivated enought to add support for such huge message
> > buffer. Therefore I suggest to limit it to 32G for now.
> 
> Yeah, I think we gonna have problems even with a 4G logbuf and a 32-bit
> user-space doing syslog(int len).
> 
> I agree on the "not motivated enough" part ;)

OK, I have pushed an updated patch that has the limit 2GB
into printk.git, for-4.20 branch.

Note that it is slightly different than the yesterday's proposal.
I made a mistake in testing and still compared with UNIT_MAX.

The pushed version can be seen at
https://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk.git/commit/?h=for-4.20&id=e6fe3e5b7d16e8f146a4ae7fe481bc6e97acde1e

Best Regards,
Petr

  reply	other threads:[~2018-10-09 13:05 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-29 16:45 [PATCH v5 1/4] printk: Fix panic caused by passing log_buf_len to command line zhe.he
2018-09-29 16:45 ` [PATCH v5 2/4] printk: Correct wrong casting zhe.he
2018-10-02  5:50   ` Sergey Senozhatsky
2018-10-08 13:03     ` Petr Mladek
2018-09-29 16:45 ` [PATCH v5 3/4] printk: Add KBUILD_MODNAME and remove a redundant print prefix zhe.he
2018-10-02  5:52   ` Sergey Senozhatsky
2018-10-08 13:04   ` Petr Mladek
2018-09-29 16:45 ` [PATCH v5 4/4] printk: Give error on attempt to set log buffer length to over 4G zhe.he
2018-10-02  5:51   ` Sergey Senozhatsky
2018-10-08 13:59   ` Petr Mladek
2018-10-08 14:59     ` Sergey Senozhatsky
2018-10-09 13:05       ` Petr Mladek [this message]
2018-10-09 13:57         ` Sergey Senozhatsky
2018-10-10  8:09           ` Petr Mladek
2018-10-10  8:21             ` Sergey Senozhatsky
2018-10-08 16:30     ` He Zhe
2018-10-02  5:48 ` [PATCH v5 1/4] printk: Fix panic caused by passing log_buf_len to command line Sergey Senozhatsky
2018-10-08 13:01 ` Petr Mladek

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