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[72.110.123.76]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35bba5a2c60sm196240a91.9.2026.03.17.11.59.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Mar 2026 12:00:01 -0700 (PDT) From: Gui-Dong Han To: gregkh@linuxfoundation.org, dakr@kernel.org, rafael@kernel.org Cc: linux-kernel@vger.kernel.org, driver-core@lists.linux.dev, intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-sound@vger.kernel.org, akaieurus@gmail.com, me@ziyao.cc, Gui-Dong Han Subject: [PATCH 0/4] debugfs: disallow NULL string creation and fix callers Date: Wed, 18 Mar 2026 02:59:09 +0800 Message-ID: <20260317185920.43387-1-hanguidong02@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-sound@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A recent bug report [1] highlighted a NULL pointer dereference when reading a debugfs string file created with a NULL pointer. The community discussed the issue and agreed that creating string nodes with NULL is invalid and should be forbidden at creation time [2]. Since no fix was submitted following the discussion, I have implemented the agreed solution. Patch 1 modifies debugfs_create_str() to reject NULL pointers, returning early and triggering a WARN_ON to expose offending callers. Patch 2 is a code hygiene fix. While modifying the file, I noticed the EXPORT_SYMBOL_GPL for debugfs_create_str() was misplaced far away from the function body. This patch moves it to the correct location. I carefully audited existing callers across the kernel tree. Some drivers passing NULL have already been independently identified and fixed [3]. The remaining two subsystems (soundwire and drm/i915) are addressed in patches 3 and 4 by initializing their respective string parameters to empty strings (""). The existing logic in both subsystems correctly and safely handles empty strings. [1] https://lore.kernel.org/lkml/17647e4c.d461.19b46144a4e.Coremail.yangshiguang1011@163.com/ [2] https://lore.kernel.org/lkml/2025122221-gag-malt-75ba@gregkh/ [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8cc27f5c6dd1 Gui-Dong Han (4): debugfs: check for NULL pointer in debugfs_create_str() debugfs: fix placement of EXPORT_SYMBOL_GPL for debugfs_create_str() soundwire: debugfs: initialize firmware_file to empty string drm/i915/display: initialize string params to empty strings drivers/gpu/drm/i915/display/intel_display_params.h | 4 ++-- drivers/soundwire/debugfs.c | 5 +++-- fs/debugfs/file.c | 7 +++++-- 3 files changed, 10 insertions(+), 6 deletions(-) -- 2.43.0