CVE-2024-49983: Double Free

In the Linux kernel, the following vulnerability has been resolved:

ext4: drop ppath from ext4_ext_replay_update_ex() to avoid double-free

When calling ext4_force_split_extent_at() in ext4_ext_replay_update_ex(), the 'ppath' is updated but it is the 'path' that is freed, thus potentially triggering a double-free in the following process:

ext4_ext_replay_update_ex ppath = path ext4_force_split_extent_at(&ppath) ext4_split_extent_at ext4_ext_insert_extent ext4_ext_create_new_leaf ext4_ext_grow_indepth ext4_find_extent if (depth > path[0].p_maxdepth) kfree(path) ---> path First freed *orig_path = path = NULL ---> null ppath kfree(path) ---> path double-free !!!

So drop the unnecessary ppath and use path directly to avoid this problem. And use ext4_find_extent() directly to update path, avoiding unnecessary memory allocation and freeing. Also, propagate the error returned by ext4_find_extent() instead of using strange error codes.