CVE-2024-49884
Severity CVSS v4.0:
Pending analysis
Type:
CWE-416
Use After Free
Publication date:
21/10/2024
Last modified:
03/11/2025
Description
In the Linux kernel, the following vulnerability has been resolved:<br />
<br />
ext4: fix slab-use-after-free in ext4_split_extent_at()<br />
<br />
We hit the following use-after-free:<br />
<br />
==================================================================<br />
BUG: KASAN: slab-use-after-free in ext4_split_extent_at+0xba8/0xcc0<br />
Read of size 2 at addr ffff88810548ed08 by task kworker/u20:0/40<br />
CPU: 0 PID: 40 Comm: kworker/u20:0 Not tainted 6.9.0-dirty #724<br />
Call Trace:<br />
<br />
kasan_report+0x93/0xc0<br />
ext4_split_extent_at+0xba8/0xcc0<br />
ext4_split_extent.isra.0+0x18f/0x500<br />
ext4_split_convert_extents+0x275/0x750<br />
ext4_ext_handle_unwritten_extents+0x73e/0x1580<br />
ext4_ext_map_blocks+0xe20/0x2dc0<br />
ext4_map_blocks+0x724/0x1700<br />
ext4_do_writepages+0x12d6/0x2a70<br />
[...]<br />
<br />
Allocated by task 40:<br />
__kmalloc_noprof+0x1ac/0x480<br />
ext4_find_extent+0xf3b/0x1e70<br />
ext4_ext_map_blocks+0x188/0x2dc0<br />
ext4_map_blocks+0x724/0x1700<br />
ext4_do_writepages+0x12d6/0x2a70<br />
[...]<br />
<br />
Freed by task 40:<br />
kfree+0xf1/0x2b0<br />
ext4_find_extent+0xa71/0x1e70<br />
ext4_ext_insert_extent+0xa22/0x3260<br />
ext4_split_extent_at+0x3ef/0xcc0<br />
ext4_split_extent.isra.0+0x18f/0x500<br />
ext4_split_convert_extents+0x275/0x750<br />
ext4_ext_handle_unwritten_extents+0x73e/0x1580<br />
ext4_ext_map_blocks+0xe20/0x2dc0<br />
ext4_map_blocks+0x724/0x1700<br />
ext4_do_writepages+0x12d6/0x2a70<br />
[...]<br />
==================================================================<br />
<br />
The flow of issue triggering is as follows:<br />
<br />
ext4_split_extent_at<br />
path = *ppath<br />
ext4_ext_insert_extent(ppath)<br />
ext4_ext_create_new_leaf(ppath)<br />
ext4_find_extent(orig_path)<br />
path = *orig_path<br />
read_extent_tree_block<br />
// return -ENOMEM or -EIO<br />
ext4_free_ext_path(path)<br />
kfree(path)<br />
*orig_path = NULL<br />
a. If err is -ENOMEM:<br />
ext4_ext_dirty(path + path->p_depth)<br />
// path use-after-free !!!<br />
b. If err is -EIO and we have EXT_DEBUG defined:<br />
ext4_ext_show_leaf(path)<br />
eh = path[depth].p_hdr<br />
// path also use-after-free !!!<br />
<br />
So when trying to zeroout or fix the extent length, call ext4_find_extent()<br />
to update the path.<br />
<br />
In addition we use *ppath directly as an ext4_ext_show_leaf() input to<br />
avoid possible use-after-free when EXT_DEBUG is defined, and to avoid<br />
unnecessary path updates.
Impact
Base Score 3.x
7.80
Severity 3.x
HIGH
Vulnerable products and versions
| CPE | From | Up to |
|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 3.18 (including) | 5.10.227 (excluding) |
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 5.11 (including) | 5.15.168 (excluding) |
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 5.16 (including) | 6.1.113 (excluding) |
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 6.2 (including) | 6.6.55 (excluding) |
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 6.7 (including) | 6.10.14 (excluding) |
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 6.11 (including) | 6.11.3 (excluding) |
To consult the complete list of CPE names with products and versions, see this page
References to Advisories, Solutions, and Tools
- https://git.kernel.org/stable/c/393a46f60ea4f249dc9d496d4eb2d542f5e11ade
- https://git.kernel.org/stable/c/448100a29395b0c8b4c42967155849fe0fbe808f
- https://git.kernel.org/stable/c/5d949ea75bb529ea6342e83465938a3b0ac51238
- https://git.kernel.org/stable/c/8fe117790b37c84c651e2bad9efc0e7fda73c0e3
- https://git.kernel.org/stable/c/915ac3630488af0ca194dc63b86d99802b4f6e18
- https://git.kernel.org/stable/c/a5401d4c3e2a3d25643c567d26e6de327774a2c9
- https://git.kernel.org/stable/c/c26ab35702f8cd0cdc78f96aa5856bfb77be798f
- https://git.kernel.org/stable/c/cafcc1bd62934547c76abf46c6d0d54f135006fe
- https://git.kernel.org/stable/c/e52f933598b781d291b9297e39c463536da0e185
- https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html
- https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html



