In the Linux kernel, the following vulnerability has been resolved:
ext4: fix use-after-free read in ext4_find_extent for bigalloc + inline
Syzbot found the following issue: loop0: detected capacity change from 0 to 2048 EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 without journal. Quota mode: none. ================================================================== BUG: KASAN: use-after-free in ext4_ext_binsearch_idx fs/ext4/extents.c:768 [inline] BUG: KASAN: use-after-free in ext4_find_extent+0x76e/0xd90 fs/ext4/extents.c:931 Read of size 4 at addr ffff888073644750 by task syz-executor420/5067
CPU: 0 PID: 5067 Comm: syz-executor420 Not tainted 6.2.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1b1/0x290 lib/dump_stack.c:106 print_address_description+0x74/0x340 mm/kasan/report.c:306 print_report+0x107/0x1f0 mm/kasan/report.c:417 kasan_report+0xcd/0x100 mm/kasan/report.c:517 ext4_ext_binsearch_idx fs/ext4/extents.c:768 [inline] ext4_find_extent+0x76e/0xd90 fs/ext4/extents.c:931 ext4_clu_mapped+0x117/0x970 fs/ext4/extents.c:5809 ext4_insert_delayed_block fs/ext4/inode.c:1696 [inline] ext4_da_map_blocks fs/ext4/inode.c:1806 [inline] ext4_da_get_block_prep+0x9e8/0x13c0 fs/ext4/inode.c:1870 ext4_block_write_begin+0x6a8/0x2290 fs/ext4/inode.c:1098 ext4_da_write_begin+0x539/0x760 fs/ext4/inode.c:3082 generic_perform_write+0x2e4/0x5e0 mm/filemap.c:3772 ext4_buffered_write_iter+0x122/0x3a0 fs/ext4/file.c:285 ext4_file_write_iter+0x1d0/0x18f0 call_write_iter include/linux/fs.h:2186 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x7dc/0xc50 fs/read_write.c:584 ksys_write+0x177/0x2a0 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f4b7a9737b9 RSP: 002b:00007ffc5cac3668 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f4b7a9737b9 RDX: 00000000175d9003 RSI: 0000000020000200 RDI: 0000000000000004 RBP: 00007f4b7a933050 R08: 0000000000000000 R09: 0000000000000000 R10: 000000000000079f R11: 0000000000000246 R12: 00007f4b7a9330e0 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 </TASK>
Above issue is happens when enable bigalloc and inline data feature. As commit 131294c35ed6 fixed delayed allocation bug in ext4_clu_mapped for bigalloc + inline. But it only resolved issue when has inline data, if inline data has been converted to extent(ext4_da_convert_inline_data_to_extent) before writepages, there is no EXT4_STATE_MAY_INLINE_DATA flag. However i_data is still store inline data in this scene. Then will trigger UAF when find extent. To resolve above issue, there is need to add judge "ext4_has_inline_data(inode)" in ext4_clu_mapped().
CVSS Details
- CVSS 3.1 Base Score: 7.8
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon Linux Ami 2 | — | Upgrade perfUpgrade kernel-headersUpgrade kernel-debuginfo-common-aarch64Upgrade kernelUpgrade kernel-tools-develUpgrade kernel-develUpgrade kernel-tools-debuginfoUpgrade kernel-debuginfoUpgrade python-perf-debuginfoUpgrade kernel-livepatch-5.15.117-72.142Upgrade python-perfUpgrade bpftool-debuginfoUpgrade kernel-toolsUpgrade kernel-livepatch-5.10.184-174.730Upgrade perf-debuginfoUpgrade bpftoolUpgrade kernel-debuginfo-common-x86_64 | May 20, 2026 | May 20, 2026 |
| Amazon_linux_2023 | — | Upgrade kernel-debuginfoUpgrade kernel-debuginfo-common-aarch64Upgrade perf-debuginfoUpgrade kernel-tools-debuginfoUpgrade perfUpgrade kernel-libbpfUpgrade kernel-toolsUpgrade kernel-headersUpgrade bpftool-debuginfoUpgrade kernel-develUpgrade kernel-debuginfo-common-x86_64Upgrade python3-perfUpgrade bpftoolUpgrade kernel-tools-develUpgrade python3-perf-debuginfoUpgrade kernel-libbpf-develUpgrade kernel-libbpf-staticUpgrade kernelUpgrade kernel-livepatch-6.1.29-47.49 | Nov 6, 2025 | Oct 22, 2025 |
| Debian | — | Upgrade linux | Oct 24, 2025 | Oct 24, 2025 |
| Huawei Euleros 2_0_sp13 | — | Upgrade bpftoolUpgrade kernel-toolsUpgrade python3-perfUpgrade kernel-abi-stablelistsUpgrade kernelUpgrade kernel-tools-libs | Feb 3, 2026 | Feb 2, 2026 |
| Ubuntu | — | Upgrade linux-nvidia-tegra-igxUpgrade linux-iotUpgrade linux-aws-5.15Upgrade linux-azureUpgrade linux-gcp-5.4Upgrade linux-nvidia-tegra-5.15Upgrade linux-gcp-fipsUpgrade linux-azure-fipsUpgrade linux-raspiUpgrade linux-raspi-5.4Upgrade linuxUpgrade linux-hwe-5.15Upgrade linux-azure-5.4Upgrade linux-awsUpgrade linux-ibm-5.4Upgrade linux-bluefieldUpgrade linux-realtimeUpgrade linux-ibm-5.15Upgrade linux-intel-iotgUpgrade linux-gcpUpgrade linux-nvidia-tegraUpgrade linux-gcp-5.15Upgrade linux-intel-iot-realtimeUpgrade linux-nvidiaUpgrade linux-lowlatencyUpgrade linux-lowlatency-hwe-5.15Upgrade linux-gkeopUpgrade linux-riscv-5.15Upgrade linux-hwe-5.4Upgrade linux-fipsUpgrade linux-aws-5.4Upgrade linux-ibmUpgrade linux-xilinx-zynqmpUpgrade linux-aws-fipsUpgrade linux-intel-iotg-5.15Upgrade linux-oracle-5.15Upgrade linux-oracle-5.4Upgrade linux-kvmUpgrade linux-oracleUpgrade linux-gkeUpgrade linux-azure-5.15 | Oct 28, 2025 | Oct 24, 2025 |
Prioritise with Active Threat Intelligence
With curated Threat Intelligence, you can see which vulnerabilities truly put you at risk, prioritize what matters most, and act before attackers do.
Explore Intelligence Hub