In the Linux kernel, the following vulnerability has been resolved:
ext4: fix null-ptr-deref in ext4_write_info
I caught a null-ptr-deref bug as follows: ================================================================== KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f] CPU: 1 PID: 1589 Comm: umount Not tainted 5.10.0-02219-dirty #339 RIP: 0010:ext4_write_info+0x53/0x1b0 [...] Call Trace: dquot_writeback_dquots+0x341/0x9a0 ext4_sync_fs+0x19e/0x800 __sync_filesystem+0x83/0x100 sync_filesystem+0x89/0xf0 generic_shutdown_super+0x79/0x3e0 kill_block_super+0xa1/0x110 deactivate_locked_super+0xac/0x130 deactivate_super+0xb6/0xd0 cleanup_mnt+0x289/0x400 __cleanup_mnt+0x16/0x20 task_work_run+0x11c/0x1c0 exit_to_user_mode_prepare+0x203/0x210 syscall_exit_to_user_mode+0x5b/0x3a0 do_syscall_64+0x59/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xa9 ==================================================================
Above issue may happen as follows: ------------------------------------- exit_to_user_mode_prepare task_work_run __cleanup_mnt cleanup_mnt deactivate_super deactivate_locked_super kill_block_super generic_shutdown_super shrink_dcache_for_umount dentry = sb->s_root sb->s_root = NULL <--- Here set NULL sync_filesystem __sync_filesystem sb->s_op->sync_fs > ext4_sync_fs dquot_writeback_dquots sb->dq_op->write_info > ext4_write_info ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2) d_inode(sb->s_root) s_root->d_inode <--- Null pointer dereference
To solve this problem, we use ext4_journal_start_sb directly to avoid s_root being used.
CVSS Details
- CVSS 3.1 Base Score: 5.5
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon Linux Ami 2 | — | Upgrade kernel-debuginfo-common-aarch64Upgrade kernel-tools-develUpgrade perf-debuginfoUpgrade bpftoolUpgrade perfUpgrade bpftool-debuginfoUpgrade kernel-develUpgrade python-perfUpgrade kernel-toolsUpgrade kernel-livepatch-5.15.75-48.135Upgrade kernel-livepatch-5.10.155-138.670Upgrade kernel-debuginfo-common-x86_64Upgrade kernel-debuginfoUpgrade kernelUpgrade kernel-tools-debuginfoUpgrade kernel-livepatch-4.14.296-222.539Upgrade python-perf-debuginfoUpgrade kernel-headers | May 20, 2026 | May 20, 2026 |
| Debian | — | Upgrade linux | Sep 18, 2025 | Sep 18, 2025 |
| Huawei Euleros 2_0_sp13 | — | Upgrade kernel-abi-stablelistsUpgrade kernel-toolsUpgrade bpftoolUpgrade kernel-tools-libsUpgrade kernelUpgrade python3-perf | Dec 12, 2025 | Dec 11, 2025 |
| Redhat_linux | — | Upgrade kernelNo solution exists | Nov 14, 2025 | Sep 16, 2025 |
| Ubuntu | — | Upgrade linux-gcp-4.15Upgrade linux-hwe-5.4Upgrade linux-azure-4.15Upgrade linux-gcp-fipsUpgrade linux-azure-5.4Upgrade linux-nvidiaUpgrade linux-intel-iotg-5.15Upgrade linux-azure-fdeUpgrade linux-xilinx-zynqmpUpgrade linux-intel-iotgUpgrade linux-lowlatency-hwe-5.15Upgrade linux-iotUpgrade linux-azureUpgrade linux-gcp-5.15Upgrade linux-azure-fde-5.15Upgrade linux-gkeopUpgrade linux-kvmUpgrade linux-oracleUpgrade linux-realtimeUpgrade linux-bluefieldUpgrade linux-aws-fipsUpgrade linux-raspiUpgrade linux-azure-5.15Upgrade linux-hwe-5.15Upgrade linux-hweUpgrade linux-ibmUpgrade linux-azure-fipsUpgrade linux-aws-5.15Upgrade linux-gcp-5.4Upgrade linux-gcpUpgrade linux-riscv-5.15Upgrade linuxUpgrade linux-awsUpgrade linux-raspi-5.4Upgrade linux-gkeUpgrade linux-ibm-5.4Upgrade linux-aws-5.4Upgrade linux-aws-hweUpgrade linux-fipsUpgrade linux-lowlatencyUpgrade linux-oracle-5.4Upgrade linux-oracle-5.15 | Sep 19, 2025 | Sep 17, 2025 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Oct 15, 2025 | Sep 16, 2025 |
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