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Date: Tue, 29 Sep 2026 19:28:44 -0700
From: Kees Cook <kees@kernel.org>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Bill Wendling <morbo@google.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Gow <david@davidgow.net>, Petr Mladek <pmladek@suse.com>,
	Shuvam Pandey <shuvampandey1@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>, nikitash.mariiaw@gmail.com,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH v2 5/9] seq_buf: Add seq_buf_strlen()
Message-ID: <202609291927.9D27E60@keescook>
References: <20260919002658.stay.929-kees@kernel.org>
 <20260919002714.4060307-5-kees@kernel.org>
 <2026091953-cherub-empty-ef35@gregkh>
 <202609191326.4042FC4@keescook>
 <2026092037-antsy-shrapnel-6139@gregkh>
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In-Reply-To: <2026092037-antsy-shrapnel-6139@gregkh>

On Sun, Sep 20, 2026 at 06:34:32AM +0100, Greg KH wrote:
> WARN on the init makes more sense, but even then it feels odd as if we
> wanted to make a seq_buf with data from a device or userspace, we would
> have to verify the size is non-zero _before_ creating the seq_buf or we
> would crash.  So someone has to check the "untrusted" data somewhere,
> right?
> 
> And why can't we have buffers of 0 size work just fine?  What prevents
> that?  People have "empty" strings for lots of things.

Yeah, okay. I'll not add the WARN for seq_buf_strlen() and remove it
from seq_buf_str().

-Kees

-- 
Kees Cook