linux-kernel - Re: [PATCH] printk: inject caller information into the body of message

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180914122217.GA518@tigerII.localdomain>
Date:   Fri, 14 Sep 2018 21:22:17 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitriy Vyukov <dvyukov@...gle.com>,
        kbuild test robot <fengguang.wu@...el.com>,
        syzkaller <syzkaller@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] printk: inject caller information into the body of
 message

On (09/14/18 21:03), Tetsuo Handa wrote:
> > 80 bytes is quite short for OOM, agreed.
> > 
> >>   static char oom_print_buf[1024];
> >>   DEFINE_PR_LINE_BUF(level, oom_print_buf);
> > 
> > Do I get it right that you suggest to drop the "size" param?
> 
> No. I just forgot to add params. ;-)
> 
> > Do OOM people agree on 1024 bytes stack usage?
> 
> I won't allocate oom_print_buf on the stack. Since its usage is serialized
> by oom_lock mutex, we don't need to allocate from stack. Since memory
> allocation request might happen when stack is already tight, we should not
> try to allocate much from stack.

... by "OOM people" I meant "MM people".
"MM people" is a subset of "OOM people".

OK, so I didn't notice the "static" part of the `oom_print_buf'.
I need some rest, I guess.

The "SMP-safe" comment becomes a bit tricky when pr_line is used with a
static buffer. Either we need to require synchronization - umm... and
document it - or to provide some means of synchronization in pr_line().
Let's think what pr_line API should do about it.

Any thoughts?

	-ss