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

Vulnerability Description

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.

References

• https://git.kernel.org/stable/c/8c26d9e53e5fbacda0732a577e97c5a5b7882aaf
• https://git.kernel.org/stable/c/a34bed978364114390162c27e50fca50791c568d
• https://git.kernel.org/stable/c/6367d3f04c69e2b8770b8137bd800e0784b0abbc
• https://git.kernel.org/stable/c/1b558006d98b7b0b730027be0ee98973dd10ee0d
• https://git.kernel.org/stable/c/3ff710662e8d86a63a39b334e9ca0cb10e5c14b0
• https://git.kernel.org/stable/c/63adc9016917e6970fb0104ee5fd6770f02b2d80
• https://git.kernel.org/stable/c/5c0f4cc84d3a601c99bc5e6e6eb1cbda542cce95