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Sun, 15 Nov 2026 13:10:19 -0800 (PST) Received: from localhost.localdomain ([112.170.44.210]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8bed1a6e7f5sm2892615b3a.25.2026.11.15.13.10.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 15 Nov 2026 13:10:17 -0800 (PST) From: Junyoung Jang To: Miklos Szeredi , Jan Kara Cc: Junyoung Jang , Amir Goldstein , Matt Bobrowski , Gwanhyun Lee , fuse-devel@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH 3/3] fanotify: zero-pad copied event names after an embedded NUL Date: Mon, 16 Nov 2026 06:09:50 +0900 Message-ID: <20261115210952.2140036-4-graypanda.inzag@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261115210952.2140036-1-graypanda.inzag@gmail.com> References: <20261115210952.2140036-1-graypanda.inzag@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit fanotify_alloc_name_event() sizes the variable-length event buffer from the qstr lengths and allocates it via kvmalloc() without zeroing. fanotify_info_copy_name() and fanotify_info_copy_name2() record name->len in info->name_len and info->name2_len, but copy the strings with strscpy(). If a qstr contains an embedded NUL byte, strscpy() stops at the first NUL and leaves the trailing bytes of the allocated name buffer uninitialized. copy_fid_info_to_user() then copies name_len + 1 bytes to userspace, leaking uninitialized kernel heap memory. This mismatch dates back to commit 929943b38daf ("fanotify: add support for FAN_REPORT_NAME") and remained after commit 0fdbe845534f ("fanotify: replace deprecated strcpy in fanotify_info_copy_{name,name2}"). Switch both helpers to strscpy_pad() so any trailing bytes up to the recorded length are zeroed. Fixes: 929943b38daf ("fanotify: add support for FAN_REPORT_NAME") Cc: stable@vger.kernel.org Co-developed-by: Gwanhyun Lee Signed-off-by: Gwanhyun Lee Signed-off-by: Junyoung Jang --- Note: default FUSE mounts report a zero fsid (-ENODEV on fanotify_mark() with FAN_REPORT_DFID_NAME), so this patch was runtime-tested on tmpfs with FAN_REPORT_DFID_NAME create and FAN_RENAME events. fs/notify/fanotify/fanotify.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h index c25cf5c1fc70..4a1f14aa4974 100644 --- a/fs/notify/fanotify/fanotify.h +++ b/fs/notify/fanotify/fanotify.h @@ -225,14 +225,14 @@ static inline void fanotify_info_copy_name(struct fanotify_info *info, return; info->name_len = name->len; - strscpy(fanotify_info_name(info), name->name, name->len + 1); + strscpy_pad(fanotify_info_name(info), name->name, name->len + 1); } static inline void fanotify_info_copy_name2(struct fanotify_info *info, const struct qstr *name) { info->name2_len = name->len; - strscpy(fanotify_info_name2(info), name->name, name->len + 1); + strscpy_pad(fanotify_info_name2(info), name->name, name->len + 1); } /* -- 2.43.0