cve/2024/CVE-2024-49881.md

### [CVE-2024-49881](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-49881)
![](https://img.shields.io/static/v1?label=Product&message=Linux&color=blue)
![](https://img.shields.io/static/v1?label=Version&message=&color=brightgreen)
![](https://img.shields.io/static/v1?label=Version&message=10809df84a4d868db61af621bae3658494165279%20&color=brightgreen)
![](https://img.shields.io/static/v1?label=Version&message=3.18%20&color=brightgreen)
![](https://img.shields.io/static/v1?label=Vulnerability&message=n%2Fa&color=blue)

### Description

In the Linux kernel, the following vulnerability has been resolved:ext4: update orig_path in ext4_find_extent()In ext4_find_extent(), if the path is not big enough, we free it and set*orig_path to NULL. But after reallocating and successfully initializingthe path, we don't update *orig_path, in which case the caller gets avalid path but a NULL ppath, and this may cause a NULL pointer dereferenceor a path memory leak. For example:ext4_split_extent  path = *ppath = 2000  ext4_find_extent    if (depth > path[0].p_maxdepth)      kfree(path = 2000);      *orig_path = path = NULL;      path = kcalloc() = 3000  ext4_split_extent_at(*ppath = NULL)    path = *ppath;    ex = path[depth].p_ext;    // NULL pointer dereference!==================================================================BUG: kernel NULL pointer dereference, address: 0000000000000010CPU: 6 UID: 0 PID: 576 Comm: fsstress Not tainted 6.11.0-rc2-dirty #847RIP: 0010:ext4_split_extent_at+0x6d/0x560Call Trace: <TASK> ext4_split_extent.isra.0+0xcb/0x1b0 ext4_ext_convert_to_initialized+0x168/0x6c0 ext4_ext_handle_unwritten_extents+0x325/0x4d0 ext4_ext_map_blocks+0x520/0xdb0 ext4_map_blocks+0x2b0/0x690 ext4_iomap_begin+0x20e/0x2c0[...]==================================================================Therefore, *orig_path is updated when the extent lookup succeeds, so thatthe caller can safely use path or *ppath.

### POC

#### Reference
No PoCs from references.

#### Github
- https://github.com/w4zu/Debian_security