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SubjectRe: [PATCH V32 27/27] tracefs: Restrict tracefs when the kernel is locked down
On Wed,  3 Apr 2019 17:32:49 -0700
Matthew Garrett <matthewgarrett@google.com> wrote:


> +static void tracefs_destroy_inode(struct inode *inode)
> +{
> + if S_ISREG(inode->i_mode)

Can we please put parenthesis around the condition. I know that the
macro has them, but no other place in the kernel plays such a trick.

if (S_ISREG(inode->i_mode))

Other than that, the rest looks good.

Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

-- Steve

> + kfree(inode->i_fop);
> +}
> +
> static int tracefs_remount(struct super_block *sb, int *flags, char *data)
> {
> int err;
> @@ -260,6 +288,7 @@ static int tracefs_show_options(struct seq_file *m, struct dentry *root)
>
> static const struct super_operations tracefs_super_operations = {
> .statfs = simple_statfs,
> + .destroy_inode = tracefs_destroy_inode,
> .remount_fs = tracefs_remount,
> .show_options = tracefs_show_options,
> };
> @@ -393,6 +422,7 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode,
> {
> struct dentry *dentry;
> struct inode *inode;
> + struct file_operations *proxy_fops;
>
> if (!(mode & S_IFMT))
> mode |= S_IFREG;
> @@ -406,8 +436,16 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode,
> if (unlikely(!inode))
> return failed_creating(dentry);
>
> + proxy_fops = kzalloc(sizeof(struct file_operations), GFP_KERNEL);
> + if (!proxy_fops)
> + return failed_creating(dentry);
> +
> + dentry->d_fsdata = fops ? (void *)fops :
> + (void *)&tracefs_file_operations;
> + memcpy(proxy_fops, dentry->d_fsdata, sizeof(struct file_operations));
> + proxy_fops->open = default_open_file;
> inode->i_mode = mode;
> - inode->i_fop = fops ? fops : &tracefs_file_operations;
> + inode->i_fop = proxy_fops;
> inode->i_private = data;
> d_instantiate(dentry, inode);
> fsnotify_create(dentry->d_parent->d_inode, dentry);

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