debugfs_create_file() takes a pointer argument that can be used during file operation callbacks (accessible via i_private in the inode structure). An obvious requirement is for the pointer to refer to valid memory when used. When creating the debugfs file to dynamically enable / disable kprobes, a pointer to local variable is passed to debugfs_create_file(); which will go out of scope when the init function returns. The reason this hasn't triggered random memory corruption is because the pointer is not accessed during the debugfs file callbacks. Since the enabled state is managed by the kprobes_all_disabled global variable, the local variable is not needed. Fix the incorrect (and unnecessary) usage of local variable during debugfs_file_create() by passing NULL instead. Link: https://lkml.kernel.org/r/163163031686.489837.4476867635937014973.stgit@devnote2
Unified · Split
| @@ -2809,13 +2809,12 @@ static const struct file_operations fops_kp = { · 2808 unmodified lines | |||
| 2809 | static int __init debugfs_kprobe_init(void) | 2809 | static int __init debugfs_kprobe_init(void) |
| 2810 | { | 2810 | { |
| 2811 | struct dentry *dir; | 2811 | struct dentry *dir; |
| 2812 | unsigned int value = 1; | ||
| 2813 | 2812 | ||
| 2814 | dir = debugfs_create_dir("kprobes", NULL); | 2813 | dir = debugfs_create_dir("kprobes", NULL); |
| 2815 | 2814 | ||
| 2816 | debugfs_create_file("list", 0400, dir, NULL, &kprobes_fops); | 2815 | debugfs_create_file("list", 0400, dir, NULL, &kprobes_fops); |
| 2817 | 2816 | ||
| 2818 | debugfs_create_file("enabled", 0600, dir, &value, &fops_kp); | 2817 | debugfs_create_file("enabled", 0600, dir, NULL, &fops_kp); |
| 2819 | 2818 | ||
| 2820 | debugfs_create_file("blacklist", 0400, dir, NULL, | 2819 | debugfs_create_file("blacklist", 0400, dir, NULL, |
| 2821 | &kprobe_blacklist_fops); | 2820 | &kprobe_blacklist_fops); |