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().
Metrics
No CVSS score has been published yet.
Affected software
| Vendor | Product | Versions |
|---|---|---|
| Linux | Linux | >= d99d714f714c9492dc64d8ab4329b083dbfa9cab, < 08d9175578d6a8e9b81921898fbf01aa669cd2be; >= f7eaacbb4e54f8a6c6674c16eff54f703ea63d5e, < 00110f3cfc9b34b2dfee2a6c9e55a0ae6df125ae; >= f7eaacbb4e54f8a6c6674c16eff54f703ea63d5e, < 3c3fac6bc0a9c00dbe65d8dc0d3a282afe4d3188 |
| Linux | Linux | 6.17 |
References
Timeline
- Published
- Nov 12, 2025
- Last modified
- Oct 19, 2026
- NVD status
- Deferred