Messages in this thread | | | From | Lisa Du <> | Subject | A race condition between debugfs and seq_file operation | Date | Mon, 8 Jun 2015 04:28:10 +0000 |
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Hi, All Recently I met one race condition related to debugfs.
Take an example from ion.c in kernel3.14: static int ion_debug_client_open(struct inode *inode, struct file *file) { return single_open(file, ion_debug_client_show, inode->i_private); }
static const struct file_operations debug_client_fops = { .open = ion_debug_client_open, .read = seq_read, .llseek = seq_lseek, .release = single_release, }; client->debug_root = debugfs_create_file(client->display_name, 0664, dev->clients_debug_root, client, &debug_client_fops);
I find during I read the debugfs node, driver can do debugfs_remove_recursive(dentry); Is it expected?
In this case, when do the seq_file read, it grabs the seq_file->lock; While in debugfs_remove_recursive(), it graps "parent->d_inode->i_mutex". So there seems no protection between the ion_debug_client_show() and debugfs_remove_recursive().
Please let me know if I didn't describe the issue clear. Would you help to comment if there's method to avoid such issue?
Best Regards.
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