linux-kernel - Re: [RFC PATCH] cmdline: Hide "debug" from /proc/cmdline

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Date:	Wed, 2 Apr 2014 22:05:12 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
	Ingo Molnar <mingo@...nel.org>, Mel Gorman <mgorman@...e.de>,
	Kay Sievers <kay@...y.org>
Subject: Re: [RFC PATCH] cmdline: Hide "debug" from /proc/cmdline

On Wed, Apr 2, 2014 at 9:50 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Wed, 2 Apr 2014, Andrew Morton wrote:
>> On Wed, 2 Apr 2014 14:42:19 -0400 Steven Rostedt <rostedt@...dmis.org> wrote:
>>
>> > It has come to our attention that a system running a specific user
>> > space init program will not boot if you add "debug" to the kernel
>> > command line. What happens is that the user space tool parses the
>> > kernel command line, and if it sees "debug" it will spit out so much
>> > information that the system fails to boot. This basically renders the
>> > "debug" option for the kernel useless.
>> >
>> > This bug has been reported to the developers of said tool
>> > here:
>> >
>> >   https://bugs.freedesktop.org/show_bug.cgi?id=76935
>> >
>> > The response is:
>> >
>> > "Generic terms are generic, not the first user owns them."
>> >
>> > That is, the "debug" statement on the *kernel* command line is not
>> > owned by the kernel just because it was the first user of it, and
>> > they refuse to fix their bug.
>> >
>> > Well, my response is, we OWN the kernel command line, and as such, we
>> > can keep the users from seeing stuff on it if we so choose. And with
>> > that, I propose this patch, which hides "debug" from /proc/cmdline,
>> > such that we don't have to worry about tools parsing for it and causing
>> > hardship for those trying to debug the kernel.
>> >
>>
>> I had to check the date on this but surprisingly, it's all post
>> April 1.
>>
>> --- a/fs/read_write.c~a
>> +++ a/fs/read_write.c
>> @@ -513,6 +513,8 @@ SYSCALL_DEFINE3(read, unsigned int, fd,
>>       struct fd f = fdget_pos(fd);
>>       ssize_t ret = -EBADF;
>>
>> +     BUG_ON(!strcmp(current->comm, "systemd"));
>
> Can we make that strncmp(current->comm, "systemd", 7) please? So we
> catch the systemd-xxx stuff as well!
>
> Otherwise Acked-by-me
>
>           tglx
> --
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While we are here, can we please also talk about the !cgroup situation?
https://bugs.freedesktop.org/show_bug.cgi?id=74589

A segfaulting systemd on CONFIG_CGROUPS=n is no fun.

-- 
Thanks,
//richard
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