UBUNTU: SAUCE: (efi-lockdown) debugfs: Disallow use of debugfs files when the kernel...

Disallow opening of debugfs files when the kernel is locked down as various
drivers give raw access to hardware through debugfs.

Accesses to tracefs should use /sys/kernel/tracing/ rather than
/sys/kernel/debug/tracing/.  Possibly a symlink should be emplaced.

Normal device interaction should be done through configfs or a miscdev, not
debugfs.

Note that this makes it unnecessary to specifically lock down show_dsts(),
show_devs() and show_call() in the asus-wmi driver.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Andy Shevchenko <andy.shevchenko@gmail.com>
cc: acpi4asus-user@lists.sourceforge.net
cc: platform-driver-x86@vger.kernel.org
cc: Matthew Garrett <matthew.garrett@nebula.com>
cc: Thomas Gleixner <tglx@linutronix.de>
(cherry picked from commit 125da2e1c5d0a6aca5faafba336c8e8506a4e000
 git://git.kernel.org/pub/scm/linux/kernel/git/jwboyer/fedora.git)
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index cd12e6576b48e306cc77dd14b4e200d5f78a7930..097be2a59c5106514bcbb4fc3b2e829b1c3687fd 100644 (file)
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -142,6 +142,10 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
        const struct file_operations *real_fops = NULL;
        int r;
 
+       if (kernel_is_locked_down("debugfs"))
+               return -EPERM;
+
+
        r = debugfs_file_get(dentry);
        if (r)
                return r == -EIO ? -ENOENT : r;
@@ -267,6 +271,9 @@ static int full_proxy_open(struct inode *inode, struct file *filp)
        struct file_operations *proxy_fops = NULL;
        int r;
 
+       if (kernel_is_locked_down("debugfs"))
+               return -EPERM;
+
        r = debugfs_file_get(dentry);
        if (r)
                return r == -EIO ? -ENOENT : r;