linux-kernel - Re: [PATCH] kobject: Fix global-out-of-bounds in kobject_action

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Date:   Tue, 7 Mar 2023 10:27:48 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Xia Fukun <xiafukun@...wei.com>
Cc:     prajnoha@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kobject: Fix global-out-of-bounds in
 kobject_action_type()

A: http://en.wikipedia.org/wiki/Top_post
Q: Were do I find info about this thing called top-posting?
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

A: No.
Q: Should I include quotations after my reply?

http://daringfireball.net/2007/07/on_top

On Tue, Mar 07, 2023 at 05:08:02PM +0800, Xia Fukun wrote:
> Thanks for your reply.
> Your understanding is correct."offline\0\0\0\0\0\0\0\0\0\0" is indeed blocked
> from matching "offline" and returns a failed result.
> 
> I'm not sure whether to relax the restrictions to make it match successfully.
> After all, the incoming count is too large and not the actual length of
> "offline".

But that doesn't matter at all.  Sometimes you do not have control over
the buffer length when writing to a file like this, what matters is the
content of the buffer and we should stop at the first \0 as that's the
"end of a string" in this type of api.

So your change here might break existing userspace code, and we can't do
that, sorry.

thanks,

greg k-h