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().
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Redhat_linux | — | No solution exists | Jul 17, 2026 | Nov 12, 2025 |
| Ubuntu | — | Upgrade linux-image-6.17.0-14-genericUpgrade linux-image-gcp-64k-6.17Upgrade linux-image-oracleUpgrade linux-image-realtimeUpgrade linux-image-oracle-6.17Upgrade linux-image-6.17.0-1007-gcp-64kUpgrade linux-image-6.17.0-1008-raspiUpgrade linux-image-generic-6.17Upgrade linux-image-6.17.0-1007-gcpUpgrade linux-image-virtualUpgrade linux-image-awsUpgrade linux-image-6.17.0-1007-awsUpgrade linux-image-6.17.0-1007-aws-64kUpgrade linux-image-oracle-64k-6.17Upgrade linux-image-gcp-6.17Upgrade linux-image-6.17.0-1011-oemUpgrade linux-image-oem-6.17Upgrade linux-image-6.17.0-14-generic-64kUpgrade linux-image-6.17.0-1006-realtimeUpgrade linux-image-gcp-64kUpgrade linux-image-genericUpgrade linux-image-azure-6.17Upgrade linux-image-aws-64k-6.17Upgrade linux-image-6.17.0-1007-oracle-64kUpgrade linux-image-aws-6.17Upgrade linux-image-6.17.0-1008-azureUpgrade linux-image-raspiUpgrade linux-image-raspi-6.17Upgrade linux-image-generic-64k-6.17Upgrade linux-image-azureUpgrade linux-image-gcpUpgrade linux-image-generic-64kUpgrade linux-image-virtual-6.17Upgrade linux-image-aws-64kUpgrade linux-image-6.17.0-1007-oracleUpgrade linux-image-realtime-6.17Upgrade linux-image-oracle-64k | Feb 13, 2026 | Feb 12, 2026 |
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