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Date: Thu, 28 May 2026 13:37:31 -0700
From: Nathan Chancellor <nathan@kernel.org>
To: Alexandre Courbot <acourbot@nvidia.com>
Cc: Miguel Ojeda <ojeda@kernel.org>, Nicolas Schier <nsc@kernel.org>,
	Boqun Feng <boqun@kernel.org>, Gary Guo <gary@garyguo.net>,
	=?iso-8859-1?Q?Bj=F6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
	Benno Lossin <lossin@kernel.org>,
	Andreas Hindborg <a.hindborg@kernel.org>,
	Alice Ryhl <aliceryhl@google.com>, Trevor Gross <tmgross@umich.edu>,
	Danilo Krummrich <dakr@kernel.org>,
	David Airlie <airlied@gmail.com>, Simona Vetter <simona@ffwll.ch>,
	John Hubbard <jhubbard@nvidia.com>,
	Alistair Popple <apopple@nvidia.com>, Timur Tabi <ttabi@nvidia.com>,
	Zhi Wang <zhiw@nvidia.com>, Eliot Courtney <ecourtney@nvidia.com>,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	rust-for-linux@vger.kernel.org, nova-gpu@lists.linux.dev,
	dri-devel@lists.freedesktop.org
Subject: Re: [PATCH v2 1/7] scripts: modpost: detect and report truncated
 buf_printf() output
Message-ID: <20260528203731.GB3100532@ax162>
References: <20260527-nova-exports-v2-0-06de4c556d55@nvidia.com>
 <20260527-nova-exports-v2-1-06de4c556d55@nvidia.com>
 <20260527171823.GA1893026@ax162>
 <DIUCC1RFFE10.1LJ15YI8ZHPOH@nvidia.com>
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In-Reply-To: <DIUCC1RFFE10.1LJ15YI8ZHPOH@nvidia.com>

On Thu, May 28, 2026 at 10:23:18PM +0900, Alexandre Courbot wrote:
> Hi Nathan,
> 
> On Thu May 28, 2026 at 2:18 AM JST, Nathan Chancellor wrote:
> > On Wed, May 27, 2026 at 08:52:17PM +0900, Alexandre Courbot wrote:
> >> buf_printf() uses a fixed-size stack buffer. vsnprintf() returns the
> >> number of bytes that *would* have been written to that buffer, which can
> >> be larger than the size of said buffer if the formatted string is too
> >> long.
> >> 
> >> The problem is that whenever this happens buf_printf() currently passes
> >> this length, unchecked, to buf_write(), which silently reads past the
> >> stack buffer and copies invalid data into the output buffer.
> >> 
> >> Fix this by detecting vsnprintf() failures and truncations before
> >> appending to the output buffer, and report a fatal error instead of
> >> producing corrupt symbol names.
> >> 
> >> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> >
> > Acked-by: Nathan Chancellor <nathan@kernel.org>
> 
> If that works for you, can you take this patch through the build tree?
> I've included it in this series because it detects the issue that the
> series fixes, but it is not a dependency for the next patches. I just
> wanted to include it for context.

Sure, I can pick this one up through the Kbuild tree.

-- 
Cheers,
Nathan