5.4-stable review patch. If anyone has any objections, please let me know.
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From: Peter Oberparleiter oberpar@linux.ibm.com
[ Upstream commit fec7bdfe7f8694a0c39e6c3ec026ff61ca1058b9 ]
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 meted@linux.ibm.com Reviewed-by: Vasily Gorbik gor@linux.ibm.com Fixes: 5496197f9b08 ("debugfs: Restrict debugfs when the kernel is locked down") Signed-off-by: Peter Oberparleiter oberpar@linux.ibm.com Signed-off-by: Alexander Gordeev agordeev@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 f4c7dbfaf8ee..c5f53dc3dbbc 100644 --- a/arch/s390/hypfs/hypfs_dbfs.c +++ b/arch/s390/hypfs/hypfs_dbfs.c @@ -64,24 +64,28 @@ 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, .llseek = no_llseek, .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); }