CVE-2024-49958: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: ocfs2: reserve space for inline xattr before attaching reflink tree One of our customers reported a crash and a corrupted ocfs2 filesystem. The crash was due to the detection of corruption. Upon troubleshooting, the fsck -fn output showed the below corruption [EXTENT_LIST_FREE] Extent list in owner 33080590 claims 230 as the next free chain record, but fsck believes the largest valid value is 227. Clamp the next record value? n The stat output from the debugfs.ocfs2 showed the following corruption where the "Next Free Rec:" had overshot the "Count:" in the root metadata block. Inode: 33080590 Mode: 0640 Generation: 2619713622 (0x9c25a856) FS Generation: 904309833 (0x35e6ac49) CRC32: 00000000 ECC: 0000 Type: Regular Attr: 0x0 Flags: Valid Dynamic Features: (0x16) HasXattr InlineXattr Refcounted Extended Attributes Block: 0 Extended Attributes Inline Size: 256 User: 0 (root) Group: 0 (root) Size: 281320357888 Links: 1 Clusters: 141738 ctime: 0x66911b56 0x316edcb8 -- Fri Jul 12 06:02:30.829349048 2024 atime: 0x66911d6b 0x7f7a28d -- Fri Jul 12 06:11:23.133669517 2024 mtime: 0x66911b56 0x12ed75d7 -- Fri Jul 12 06:02:30.317552087 2024 dtime: 0x0 -- Wed Dec 31 17:00:00 1969 Refcount Block: 2777346 Last Extblk: 2886943 Orphan Slot: 0 Sub Alloc Slot: 0 Sub Alloc Bit: 14 Tree Depth: 1 Count: 227 Next Free Rec: 230 ## Offset Clusters Block# 0 0 2310 2776351 1 2310 2139 2777375 2 4449 1221 2778399 3 5670 731 2779423 4 6401 566 2780447 ....... .... ....... ....... .... ....... The issue was in the reflink workfow while reserving space for inline xattr. The problematic function is ocfs2_reflink_xattr_inline(). By the time this function is called the reflink tree is already recreated at the destination inode from the source inode. At this point, this function reserves space for inline xattrs at the destination inode without even checking if there is space at the root metadata block. It simply reduces the l_count from 243 to 227 thereby making space of 256 bytes for inline xattr whereas the inode already has extents beyond this index (in this case up to 230), thereby causing corruption. The fix for this is to reserve space for inline metadata at the destination inode before the reflink tree gets recreated. The customer has verified the fix.

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected Products

Vendor	Product	Versions
linux	linux_kernel	3.0.87 — 3.2
linux	linux_kernel	3.2.49 — 3.4
linux	linux_kernel	3.4.54 — 3.9
linux	linux_kernel	3.9.11 — 3.10
linux	linux_kernel	3.10.2 — 3.11
linux	linux_kernel	3.11 — 5.10.227
linux	linux_kernel	5.11 — 5.15.168
linux	linux_kernel	5.16 — 6.1.113
linux	linux_kernel	6.2 — 6.6.55
linux	linux_kernel	6.7 — 6.10.14
linux	linux_kernel	6.11 — 6.11.3

References

Advisories & Patches

https://git.kernel.org/stable/c/020f5c53c17f66c0a8f2d37dad27ace301b8d8a1 https://git.kernel.org/stable/c/5c2072f02c0d75802ec28ec703b7d43a0dd008b5 https://git.kernel.org/stable/c/5ca60b86f57a4d9648f68418a725b3a7de2816b0 https://git.kernel.org/stable/c/637c00e06564a945e9d0edb3d78d362d64935f9f https://git.kernel.org/stable/c/96ce4c3537114d1698be635f5e36c62dc49df7a4 https://git.kernel.org/stable/c/9f9a8f3ac65b4147f1a7b6c05fad5192c0e3c3d9 https://git.kernel.org/stable/c/aac31d654a0a31cb0d2fa36ae694f4e164a52707

Other References

https://git.kernel.org/stable/c/5c9807c523b4fca81d3e8e864dabc8c806402121 https://git.kernel.org/stable/c/74364cb578dcc0b6c9109519d19cbe5a56afac9a https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html

Frequently Asked Questions

What is CVE-2024-49958? +

In the Linux kernel, the following vulnerability has been resolved: ocfs2: reserve space for inline xattr before attaching reflink tree One of our customers reported a crash and a corrupted ocfs2 filesystem. The crash was due to the detection of corruption. Upon troubleshooting, the fsck -fn output showed the below corruption [EXTENT_LIST_FREE] Extent list in owner 33080590 claims 230 as the next free chain record, but fsck believes the largest valid value is 227. Clamp the next record value? n The stat output from the debugfs.ocfs2 showed the following corruption where the "Next Free Rec:" had overshot the "Count:" in the root metadata block. Inode: 33080590 Mode: 0640 Generation: 2619713622 (0x9c25a856) FS Generation: 904309833 (0x35e6ac49) CRC32: 00000000 ECC: 0000 Type: Regular Attr: 0x0 Flags: Valid Dynamic Features: (0x16) HasXattr InlineXattr Refcounted Extended Attributes Block: 0 Extended Attributes Inline Size: 256 User: 0 (root) Group: 0 (root) Size: 281320357888 Links: 1 Clusters: 141738 ctime: 0x66911b56 0x316edcb8 -- Fri Jul 12 06:02:30.829349048 2024 atime: 0x66911d6b 0x7f7a28d -- Fri Jul 12 06:11:23.133669517 2024 mtime: 0x66911b56 0x12ed75d7 -- Fri Jul 12 06:02:30.317552087 2024 dtime: 0x0 -- Wed Dec 31 17:00:00 1969 Refcount Block: 2777346 Last Extblk: 2886943 Orphan Slot: 0 Sub Alloc Slot: 0 Sub Alloc Bit: 14 Tree Depth: 1 Count: 227 Next Free Rec: 230 ## Offset Clusters Block# 0 0 2310 2776351 1 2310 2139 2777375 2 4449 1221 2778399 3 5670 731 2779423 4 6401 566 2780447 ....... .... ....... ....... .... ....... The issue was in the reflink workfow while reserving space for inline xattr. The problematic function is ocfs2_reflink_xattr_inline(). By the time this function is called the reflink tree is already recreated at the destination inode from the source inode. At this point, this function reserves space for inline xattrs at the destination inode without even checking if there is space at the root metadata block. It simply reduces the l_count from 243 to 227 thereby making space of 256 bytes for inline xattr whereas the inode already has extents beyond this index (in this case up to 230), thereby causing corruption. The fix for this is to reserve space for inline metadata at the destination inode before the reflink tree gets recreated. The customer has verified the fix. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2024-49958? +

CVE-2024-49958 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2024-49958? +

CVE-2024-49958 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2024-49958? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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