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Wed, 27 May 2026 23:18:37 -0700 (PDT) Date: Thu, 28 May 2026 09:18:34 +0300 From: Dan Carpenter To: Sean Anderson Cc: Laurent Pinchart , Tomi Valkeinen , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Michal Simek , dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org Subject: Re: [PATCH] drm: zynqmp_dp: Fix uninitialized variable in debugfs() Message-ID: References: <935aaec5-5417-3cde-f944-3c04ffbd3458@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <935aaec5-5417-3cde-f944-3c04ffbd3458@linux.dev> On Wed, May 27, 2026 at 08:31:59PM -0400, Sean Anderson wrote: > On 5/25/26 03:16, Dan Carpenter wrote: > > If the *ppos is non-zero then simple_write_to_buffer() will not > > initialize the start of the buf[] buffer. It doesn't really make sense > > to allow non-zero values for *ppos, so check for that at the start and > > return -EINVAL. > > non-zero ppos seems to be handled properly by simple_write_to_buffer. > It's not an overflow bug, it's an uninitialized variable bug. The simple_write_to_buffer() is designed to handle partial writes so it leaves the first "written" (scare quotes) part of the string as is. But in this case, we can't handle a partial write and the first part of buf[] is left uninitialized. https://staticthinking.wordpress.com/2026/05/23/simple_write_to_buffer-is-complicated/ Also this appears to be dead code since fops_zynqmp_dp_pattern is never used. regards, dan carpenter