linux-kernel - Re: [PATCH v5 4/4] printk: Give error on attempt to set log buffer length to over 4G

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Date:   Mon, 8 Oct 2018 23:59:50 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     zhe.he@...driver.com, sergey.senozhatsky@...il.com,
        rostedt@...dmis.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 4/4] printk: Give error on attempt to set log buffer
 length to over 4G

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 ;)

	-ss