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

ext4: fix potential null deref in ext4_mb_init()

In ext4_mb_init(), ext4_mb_avg_fragment_size_destroy() may be called
when sbi->s_mb_avg_fragment_size remains uninitialized (e.g., if groupinfo
slab cache allocation fails). Since ext4_mb_avg_fragment_size_destroy()
lacks null pointer checking, this leads to a null pointer dereference.

==================================================================
EXT4-fs: no memory for groupinfo slab cache
BUG: kernel NULL pointer dereference, address: 0000000000000000
PGD 0 P4D 0
Oops: Oops: 0002 [#1] SMP PTI
CPU:2 UID: 0 PID: 87 Comm:mount Not tainted 6.17.0-rc2 #1134 PREEMPT(none)
RIP: 0010:_raw_spin_lock_irqsave+0x1b/0x40
Call Trace:
<TASK>
xa_destroy+0x61/0x130
ext4_mb_init+0x483/0x540
__ext4_fill_super+0x116d/0x17b0
ext4_fill_super+0xd3/0x280
get_tree_bdev_flags+0x132/0x1d0
vfs_get_tree+0x29/0xd0
do_new_mount+0x197/0x300
__x64_sys_mount+0x116/0x150
do_syscall_64+0x50/0x1c0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
==================================================================

Therefore, add necessary null check to ext4_mb_avg_fragment_size_destroy()
to prevent this issue. The same fix is also applied to
ext4_mb_largest_free_orders_destroy().
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Fri, 14 Nov 2025 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

threat_severity

Moderate


Wed, 12 Nov 2025 23:00:00 +0000

Type Values Removed Values Added
First Time appeared Linux
Linux linux Kernel
Vendors & Products Linux
Linux linux Kernel

Wed, 12 Nov 2025 10:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: ext4: fix potential null deref in ext4_mb_init() In ext4_mb_init(), ext4_mb_avg_fragment_size_destroy() may be called when sbi->s_mb_avg_fragment_size remains uninitialized (e.g., if groupinfo slab cache allocation fails). Since ext4_mb_avg_fragment_size_destroy() lacks null pointer checking, this leads to a null pointer dereference. ================================================================== EXT4-fs: no memory for groupinfo slab cache BUG: kernel NULL pointer dereference, address: 0000000000000000 PGD 0 P4D 0 Oops: Oops: 0002 [#1] SMP PTI CPU:2 UID: 0 PID: 87 Comm:mount Not tainted 6.17.0-rc2 #1134 PREEMPT(none) RIP: 0010:_raw_spin_lock_irqsave+0x1b/0x40 Call Trace: <TASK> xa_destroy+0x61/0x130 ext4_mb_init+0x483/0x540 __ext4_fill_super+0x116d/0x17b0 ext4_fill_super+0xd3/0x280 get_tree_bdev_flags+0x132/0x1d0 vfs_get_tree+0x29/0xd0 do_new_mount+0x197/0x300 __x64_sys_mount+0x116/0x150 do_syscall_64+0x50/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e ================================================================== Therefore, add necessary null check to ext4_mb_avg_fragment_size_destroy() to prevent this issue. The same fix is also applied to ext4_mb_largest_free_orders_destroy().
Title ext4: fix potential null deref in ext4_mb_init()
References

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2025-11-12T10:23:18.449Z

Reserved: 2025-04-16T07:20:57.168Z

Link: CVE-2025-40119

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2025-11-12T11:15:41.237

Modified: 2025-11-12T16:19:12.850

Link: CVE-2025-40119

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-11-12T00:00:00Z

Links: CVE-2025-40119 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2025-11-12T22:12:29Z