From fec7bdfe7f8694a0c39e6c3ec026ff61ca1058b9 Mon Sep 17 00:00:00 2001 From: Peter Oberparleiter Date: Thu, 21 Aug 2025 14:35:40 +0200 Subject: [PATCH] s390/hypfs: Avoid unnecessary ioctl registration in debugfs Currently, hypfs registers ioctl callbacks for all debugfs files, despite only one file requiring them. This leads to unintended exposure of unused interfaces to user space and can trigger side effects such as restricted access when kernel lockdown is enabled. Restrict ioctl registration to only those files that implement ioctl functionality to avoid interface clutter and unnecessary access restrictions. Tested-by: Mete Durlu Reviewed-by: Vasily Gorbik Fixes: 5496197f9b08 ("debugfs: Restrict debugfs when the kernel is locked down") Signed-off-by: Peter Oberparleiter Signed-off-by: Alexander Gordeev --- arch/s390/hypfs/hypfs_dbfs.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/arch/s390/hypfs/hypfs_dbfs.c b/arch/s390/hypfs/hypfs_dbfs.c index 5d9effb0867cd..e74eb8f9b23a5 100644 --- a/arch/s390/hypfs/hypfs_dbfs.c +++ b/arch/s390/hypfs/hypfs_dbfs.c @@ -66,23 +66,27 @@ static long dbfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg) long rc; mutex_lock(&df->lock); - if (df->unlocked_ioctl) - rc = df->unlocked_ioctl(file, cmd, arg); - else - rc = -ENOTTY; + rc = df->unlocked_ioctl(file, cmd, arg); mutex_unlock(&df->lock); return rc; } -static const struct file_operations dbfs_ops = { +static const struct file_operations dbfs_ops_ioctl = { .read = dbfs_read, .unlocked_ioctl = dbfs_ioctl, }; +static const struct file_operations dbfs_ops = { + .read = dbfs_read, +}; + void hypfs_dbfs_create_file(struct hypfs_dbfs_file *df) { - df->dentry = debugfs_create_file(df->name, 0400, dbfs_dir, df, - &dbfs_ops); + const struct file_operations *fops = &dbfs_ops; + + if (df->unlocked_ioctl) + fops = &dbfs_ops_ioctl; + df->dentry = debugfs_create_file(df->name, 0400, dbfs_dir, df, fops); mutex_init(&df->lock); } -- 2.39.5