Bug#934304: linux-image-5.2.0-2-amd64: powertop aborts on version 5.2

[Bernhard Übelacker <bernhardu@mailbox.org>]

Dear Maintainer,
this issue seems to start since patch:
    features/all/lockdown/0031-tracefs-Restrict-tracefs-when-the-kernel-is-locked-d.patch

Therefore a vanialla build does not show this issue.

With either of the following changes on top of all
debian patches, the exception does not happen.

But the first does also prevent opening the file
when not locked down.

The second allows to open the file, but cannot say
if the intended effect of the patch for lockdowned
kernels is still given.

Kind regards,
Bernhard



diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 338c791c9a0e..f446977bf9c8 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -41,6 +41,8 @@ static int default_open_file(struct inode *inode, struct file *filp)
                return -EPERM;
 
        real_fops = dentry->d_fsdata;
+       if (!real_fops->open)
+               return -EINVAL;
        return real_fops->open(inode, filp);
 }
 



diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 338c791c9a0e..d37c959291ab 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -438,7 +438,7 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode,
 
        dentry->d_fsdata = (void *)fops;
        memcpy(proxy_fops, fops, sizeof(*proxy_fops));
-       proxy_fops->open = default_open_file;
+       proxy_fops->open = fops->open ? default_open_file : NULL;
        inode->i_mode = mode;
        inode->i_fop = proxy_fops;
        inode->i_private = data;